Of all the mass-released ROCKY HORROR albums to choose from, there are....
The movie soundtrack - Just the songs from the movie
The 25 Anniversary movie soundtrack - Almost the entire movie, dialogue and songs
London (1973) - My least favorite of the recordings, Tim Curry sounds SO different... nothing like on the movie or the Roxy doesn't include a lot of the songs that wound up in the show's score by the time the movie rolled around.
Studio (1995) - Kim Criswell is Janet, she's pretty good. This is a good recording, the actors sing the parts very well; and it's nice to hear the score, as is, with other actors than Tim Curry, Richard O'Brien, Meat Loaf, etc. and others that roll over onto several recordings.
Broadway Revival (2000) - I personally think this is the most enjoyable to listen to out of all the recordings. It's fresh, and the most fast and up-tempo'ed of all the RHS cast albums. Plus, it has the strongest cast out of any that is recorded.
Roxy/Los Angeles Cast (1974 - also serves as OBC) - This and the Broadway revival are my favorites. If you want the score without all the bells and whistles, this is what you want.
Australia (1980... I believe is the year) - Only has 6 songs. I don't really listen, but was given as a gift. Nice quality, but nowhere close to a complete score.
And if she'll say, "My darling, I'm yours!" I'll throw away my striped tie and my best pressed tweed, all I really need is the girl...