I guess now that another decade has passed (,ore or less) I should update the list and maybe revisit some former choices.
Remember - These are just my suggestions for a core library; a guideline based on my own listening experience. Not an absolute by any means!
1900 - 1920s :
BABES IN TOYLAND (studio cast on Decca) _STILL The only version available
MERRY WIDOW (studio cast on DRG) - I actually prefer the NYCO CD with Beverly Sills but it is very hard to find.
LADY BE GOOD (Studio cast on Nonesuch)- Still a delight!
THE STUDENT PRINCE (studio cast on DRG)- Still the preferred version
NO NO NANETTE (1971 Broadway revival on Sony) - Unbeatable!
OH, KAY! (studio cast on Nonesuch) -
THE DESERT SONG (studio cast on Decca) - The old Columbia Lp with Nelson eddy is also worth investigating.
SHOW BOAT (complete recording on 3 CD set from EMI)- Still the best and most complete.
GOOD NEWS (Studio cast on Jay)- Not that there are many alternate choices but this will do.
THE NEW MOON (Concert cast on Ghostlight) - Well worth getting. What a great score!
1930s :
STRIKE UP THE BAND (studio cast on Nonesuch) - It's actually the original 1928 version recorded here but it is all we have of this score.
GIRL CRAZY (Studio cast on Nonesuch) - Still the best, far better that the old Mary Martin disc.
OF THEE I SING (1952 revival cast on DRG) - The concert version from 1986 is more complete but this one plays so much better, thanks to a streamlined score. (A lot of the repetition has been removed, for the better.)
PARDON MY ENGLISH (studio cast on Nonesuch) - Lesser Gershwin but still worth investigating. This is the only recording of this show.
ANYTHING GOES (studio cast on EMI) - This version preserves the original score as heard in 1934. Alternates with interpolations are on Epic (Eileen Rogers) and RCA (Patti Lupone)
PORGY AND BESS (complete on 3 Cd's from RCA)- No other recording ha tapped this 1976 set.
ON YOUR TOES (1983 revival cast on Jay)- The 1954 revival cast on MCA is also good but this is more complete and has better sound.
BABES IN ARMS (studio cast on New World) - some prefer the DRG Encores cast, but I like the orchestral playing on this disc better. Mary Martin's disc is fun but hardly authentic.
BOYS FROM SYRACUSE (Concert cast on DRG) - A delight from start to finish. DRG also reissued Capitol's off-Broadway cast album from 1963 (recommended) and Sony has the old Jack Cassidy studio version (Not so good.)
TOO MANY GIRLS (studio cast on Painted Smiles) - It's a little hard to find but worth checking out.
1940s:
PAL JOEY (studio cast on Sony)- Also worth checking out is the Encores cast with Lupone and Gallagher.
LADY IN THE DARK (London cast on Jay)- This is the most complete and most theatrical album. Gertrude Lawrence and Danny Kare recorded some 78's of the original and they are out in the Prism label.
OKLAHOMA! (Original Broadway cast on Decca) - The original has a freshness that other recordings lack. The movie soundtrack is well sung. The most complete is the 1998 London cast with Hugh Jackman.
ON THE TOWN (studio cast on Sony) - No other ON TEH TWON touches this one.
CAROUSEL (1993 London cast on RCA) - This is the most complete. The best sung is the movie soundtrack (Gordon MacRae) and the most theatrical is the Lincoln Center cast from 1965 with John Raitt.
ANNIE GET YOUR GUN (1966 revival cast on RCA)- Merman in top form here. If you can't handle Ethel in the role try Kim Criswell (EMI) or Judy Kaye (JAY.)
FINIAN'S RAINBOW (1960 revival cast on RCA) - The new revival cast (PS Classics) is more complete and very well performed.
BRIGADOON (studio cast on DRG) - This is still my preferred BRIGADOON. EMI's studio cat with Brent Barrett is also worth checking out.
KISS ME KATE (original Broadway & studio cast on EMI) - both have the same cast and almost the same text. EMI's version was redone in stereo in 1959.
SOUTH PACIFIC (original Broadway cast on Sony)- The sound may be a bit brittle but the incandescent performances of the original cast shine through. For better sound and a more complete reading go to the 2008 revival cast (Masterwoks Broadway)
1950s:
GUYS AND DOLLS (1992 revival cast on RCA)- Jay has a note complete studio cast set, but this one has more sparkle.
THE KING AND I (1977 revival cast on RCA)- Yul Brynner heads a terrific cast here. The film soundtrack is also recommended for the sumptuous orchestrations.
PETER PAN (original Broadway cast on RCA) - Mary Martin owns this role. But Cathy Rigby offers a worthwhile alternate, and in stereo.
THE PAJAMA GAME (original Broadway cast on Sony)- The film soundtrack has Doris Day, and includes more dance music. ON balance it drops the Overture and three songs.
DAMN YANKEES (original Broadway cast on RCA)- The original is still the best, but Mercury's revival cast from 1994 delivers a potted version of the whole show.
MY FAIR LADY (original Broadway cast on Sony)- No subsequent recording comes close to the sheer perfection heard here.
WEST SIDE STORY (original Broadway cast on Sony)- The original is still the best but the movie soundtrack has those beefed up orchestrations and the new revival cast is also worthwhile. Ignore the others.
MUSIC MAN (original Broadway cast on EMI) - Some prefer the Stroman revival but she tried to hard to copy the movie. The actual film soundtrack is marred by horrible sound quality.
GYPSY (original Broadway cast on Sony) - Merman at her very best. After that you can choose from Lansbury, Daly, Peters and Lupone with the latter being my 2nd choice. Ther are also soundtracks of the two film versions but neither makes a good overall listen.
SOUND OF MUSIC (original Broadway cast on Sony) - Everyone on the planet already has the film soundtrack. The original is still one of Columbia's best cast albums.
1960s:
CAMELOT (original Broadway cast on Sony) - No other recording matches the magic and majesty of the original.
BYE BYE BIRDIE (original Broadway cast on Sony) - The film and Tv soundtracks make too many changes, and the London cast is badly sung.
HOW TO SUCCEED IN BUSINESS... (original Broadway cast on RCA) - I have a slight preference for the Matthew Broderick revival cast. Avoid the film soundtrack at all costs.
HELLO DOLLY! (original Broadway cast on RCA) - Channing's remake in 1994 is all but unlistenable. Of the alternate Dollys Mary Martin comes off best on records. Striesand sings it well on the film soundtrack but the rest of the cast is terrible.
FUNNY GIRL (original cast on Angel) - The original cast offer a lively performance. The film soundtrack is almost entirely a showcase for Streisand alone.
FIDDLER ON THE ROOF (original Broadway cast on RCA) The London cast with Topol is also quite good, adn I find teh 2004 revival cast quite enjoyable.
MAN OF LA MANCHA (original Broadway cast on Decca)- JAY offers the complete show on 2 CD's but the original cast has never been bettered.
MAME (original Broadway cast on Sony)- No other choice here.
CABARET (original Broadway cast on Sony) - The revival cast from 1998 is also excellent, but here you get Jack Gilford's "Meeskite" and Joel Grey as the MC.
HAIR (original Broadway cast on RCA)- The new revival cast has better sound and is more complete.
1970s:
COMPANY (original Broadway cast on Sony) - THe original is still the best but the Raul Esparza revival cast runs a close second.
FOLLIES (1985 concert cast on RCA) - The Papermill playhouse cast recording is also excellent and includes many of the cut songs. Angel's CD of the OCR is essential, but as we all know heavily abridged. Avoid the heavily revised London cast.
GREASE (original Broadway cast on M-g-M) - It's about time we had a new complete recording. The recent revival doesn't cut it for me. (I have never heard the John Barrowman studio cast disc on JAY.)
A LITTLE NIGHT MUSIC (original Broadway cast on Sony) - The original is something special and so well sung. The 1996 Judi Dench version is (has been) my #2 choice but when the new CD comes out next month that may change. Stay tuned...
A CHORUS LINE (original Broadway cast on Sony)- The original cast give the best performance, but actually the 2006 revival is more complete and closer to how the show plays on stage.
CHICAGO (original Broadway cast on Arista) - The original is great, but not as complete as the later discs. I prefer the London cast over the 1996 Broadway cast.
PIPPIN (original Broadway cast on Decca) - Decca's CD makes the case for this as Schwartz's best score, even if the show that contains it is a mess.
ANNIE (original Broadway cast on Sony)- The original cast is unmatchable, but the recent Time Life 2 CD set is very well performed and includes a disc of ANNIE 2 for those curious about that score.
EVITA (original Broadway cast on Decca)- Lupone and Patinkin. No question.
SWEENEY TODD (original Broadway cast on RCA) - The original cast is still the most satisfying listen over the heavily abridged revival cast and the much altered film adaptation.
1980s:
42ND STREET (original Broadway cast on RCA) - The revival cast has better sound (hopefully this original will get remastered as it could potentially blow the revival cast out of the water if done with care) but the 2001 cast album is more complete.
MERRILY WE ROLL ALONG (original Broadway cast on RCA) - Though the authors have revised the show, the origial version plays better on disc.
DREAMGIRLS (Concert cast on Nonesuch)- The reissued cast album restores some material cut from the original LP/CD editions but is still incomplete. I actually find the film soundtrack even more satisfying.
NINE (original Broadway cast on Sony)- The 2 CD set is immaculate. The closest competitor would be the 2003 revival cast.
CATS (original Broadway cast on Geffen) - The single disc of highlights is all you really need unless you are a fan of the show. (Is anybody a fan of this show?)
SUNDAY IN THE PARK WITH GEORGE (original Broadway cast on RCA)- The PS Classics 2-disc set of the revival is also good but there is something magical about Peters and Patinkin on the original 1984 recording.
LES MISERABLES (complete recording on First Night)- The concert version covers most of the material (and has Colm Wilkinson) on 2 discs, but if you want the whole show this is the set to get.
INTO THE WOODS (original Broadway cast on RCA) - Np contest here. The original is far better than the London cast or the 2002 revival.
GRAND HOTEL (original Broadway cast on RCA)- Though the recording is not as well produced as it could have been, it still does a good job showcasing Maury Yeston's ingenious reworking of the Wright/Forrest material combined with a handful of his own songs. Credit Wally Harper for making it all sound of one piece.
CITY OF ANGELS (original Broadway cast on Columbia) - A lively, jazzy score showing Cy Coleman at his very best. (Two other Coleman scores worth listening to: SWEET CHARITY and ON THE 20th CENTURY.)
1990s:
MISS SAIGON (Complete recording on EMI) - Your choice here depends on whether you want the complete score on this set or a better cast with the original London company.
THE SECRET GARDEN (original Broadway cast on Columbia)- The Australian cast is better but limited to just 8 highlights this becomes the default winner.
CRAZY FOR YOU (original Broadway cast on EMI)- The Broadway cast serves the material better than the London cast - but only slightly.
BLOOD BROTHERS (original London cast on RCA) - There is also a good version with Petula Clark and the Cassidy brothers, but this one really captures the show.
KISS OF THE SPIDER WOMAN (original Broadway cast on RCA) - Chita Rivera and Brent Carver give star power to this set. Mercury's edition with Vanessa Williams presents a potted version of the entire show.
PASSION (original Broadway cast on EMI)- Sondheim's most hauntingly beautiful score. The London cast has a little more of the show but the female leads can't match Murphy and Mazzie.
RENT (original Broadway cast on Geffen) - No disc but this one.
TITANIC (original Broadway cast on RCA) - Despite the low levels this is a very enjoyable recording.
STEEL PIER (original Broadway cast on RCA) - Though the show was a critical and commercial flop, this is one of Kander and Ebb's better scores. And the cast album is exceptionally well produced.
RAGTIME (original Broadway cast on RCA) - This 2 CD set of the entire score is topped up with an 8-minute orchestral suite. One of the best scores of the 1990s.
2000:
THE FULL MONTY (original cast on RCA) - The score is uneven but enough gems to make it worthwhile.
THE PRODUCERS (original Broadway cast on Sony) - Musical comedy comes back to Broadway with a roar. You can follow the show just by listening to this sparking OCR.
HAIRSPRAY (original Broadway cast on Sony)- Though teh original cast is quite winning, the film soundtrack actually gioes it one better.
AVENUE Q (original cast on RCA) - A very funny show and a cast album that captures that fun.
WICKED - Still running but this OCR is easily the most successful cast album of the decade.
THE LIGHT IN THE PIAZZA (original Broadway cast on Nonesuch) - a rich evocative score by Adam Guettel that gets better with each listen.
DIRTY ROTTEN SCOUNDRELS (original Broadway cast on Ghostlight) - a lively, fun score with some tuneful tunes.
GREY GARDENS (original Broadway cast on PS Classics) - This is something special. If you can, get both recordings as neither has everything.
SPRING AWAKENING (original cast on Decca) - I do wish the recording captured the show better, but this was one of the decades most exciting new arrivals.
IN THE HEIGHTS (original cast on Ghostlight) - The 2-disc set may overstay its welcome a bit, but the show heralds a new talent.
Notable off-Broadway productions:
THREEPENNY OPERA(1954 revival on Decca)- ArkivMusik now offers the 1976 revival which has a more literal translation.
THE GOLDEN APPLE (original cast on RCA) - Heavily abridged but it's still the only recording we have of this delectable score.
THE FANTASTICKS (original cast on Decca) - The revival cast on Ghostlight has better sound, but the original has Jerry Orbach!
YOU'RE A GOOD MAN CHARLIE BROWN (original cast on Decca) - The revival cast on RCA is actually a better produced album.
GODSPELL (original cast on Arista) - The movie soundtrack has better sound and a wonderful new song, "Beautiful City."
MARCH OF THE FALSETTOS & FALSETTOLAND (original cast on DRG)- Two shows later combined for Falsettos.
ONCE ON THIS ISLAND (original cast on RCA) - I enjoy this CD so much I have never bothered to seek out the London cast. Anyone know if it is worth getting?
ASSASSINS (original cast on RCA) - The 2004 Broadway revival on PS Classics is also highly recommended.
THE LAST FIVE YEARS (original cast on Sh-k-Boom) - A huge cult has spring up around this show, and it deserves the growing popularity.
URINETOWN (original cast on RCA) - Has no alternates verions. Not that any are needed.
and some notable flops (1950-1999)
A TREE GROWS IN BROOKLYN (original cast on Sony)- The show may not work on stage but a very fine cast album of a score very much influenced by Rodgers and Hammerstein.
PAINT YOUR WAGON (original cast on RCA) - Many hit songs in the score of this overlooked flop. An ever better collection of highlights is on AN EVENING WITH LERNER AND LOEWE with a cast headed by Jan Peerce, Robert Merrill and Jane Powell.
CANDIDE (original cast on Sony)- So many revival and revisions but the score is best served by the original cast.
GOLDILOCKS (original cast on Sony)- Elaine Stritch in feisty, fine form.
SAIL AWAY - (original London cast on Fynbsworth Alley) -Another showcase for Stritch with a great Noel Coward score.
SUBWAYS ARE FOR SLEEPING (Original cast on Fynsworth Alley) - a really bad show with a really good score.
ANYONE CAN WHISTLE (original cast on Sony)- Can anyone believe this only lasted 9 performances? Apparently over 10,000 people attended the last performance.
DEAR WORLD (original cast on Sony) and MACK AND MABEL (original cast on MCA) shows Jerry Herman doing what he does best. The later London cast of MACK AND MABEL is also good.
PARADE (original cast on RCA) - The OCR is great but a new 2 CD set from London is much more complete, and slightly revised.
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com