Uh, yeah, I was beginning to worry about the SDMB when no one mentioned Sweeney Todd until half the thread went by. I won’t even dignify the idea that the music is tuneless. Johanna, tuneless? My Friends, Ballad of Sweeney Todd, Green Finch and Linnet Bird, freakin’ NOT WHILE I’M AROUND, tuneless? It is to laugh. True, it’s more of an opera in style, and if you’re looking for a peppy four bar melody with standard verse and chorus, you ain’t gonna get it in Sweeney (or much of Sondheim, though he does offer a few now and then). But the music is fucking glorious, the lyrics genius, the story gripping and heartbreaking.
If you only know ST from the movie, for God’s sake do yourself a favor and see a live version, or at least the Angela Lansbury/George Hearn video. Although the film’s use of full orchestra rocked hard, the score was castrated due to time, the lack of vocalists (don’t get me started on Helena Bonham Carter), and the horrific decision to cut the chorus – IMO an act of barbarism on par with anything Sweeney Todd did. 
But I’ll accept West Side Story in a tie with Sweeney. WSS is … oh my. So much awesome. WSS will always have my heart.
Kudos to the choice of 1776. I think it makes a better movie, actually, but it’s definitely the thinking person’s choice for top five. The book is stronger than the music, which is a rarity, I think.
The King and I is fabulous and very dear to me. And in a completely personal, nostalgic choice that I can’t really defend on any level except that I grew up rockin’ out to it, I will also pipe up for Jesus Christ Superstar.
Finally, Les Mis leaves me utterly cold. It’s the same four songs repeated endlessly. But I have to acknowledge the impact it has on other people, so I respect the choice from others. Wouldn’t see it again unless I was paid for the privilege … or unless my boy Drew Sarich went back to play ValJean on Broadway.