Yes, I agree with all of the obligatory responses, most notably
PHANTOM
I can't believe someone listed THE GRAPES OF WRATH! That was one (actually two, because I went back to see it again) of my most favorite experiences of seeing a Broadway show. The acting (Gary Sinise, Terry Kinney, Lois Smith, Sally Murphy) was phenomenal. Amazing ensemble cast. Wonderful direction, set design, lighting, etc. The final sequence with Rose of Shar'n breast feeding the dying man in the barn knocked my socks off with one of the slowest fades to black ever! It made me (and the entire audience) leap to its feet.
Fortunately, PBS recorded this Tony-winning production, but on the same note, it's unfortunate that the direction of the televised version lost a lot of the magic of seeing it live. The way it was shot, you couldn't see the set and how cleverly it was designed.
Oh, one more completely overrated show...
SUNSET BOULEVARD (also known as "The Worst BEST MUSICAL Ever!)
Itty Bitty Geisha?
Toyland?
Gypsy Pasadoble?
Just a few popular favorites...