Wow...well, I haven't seen all that many. If I love the music and have seen exercepts online, does that count as watching the musicals?
At the moment, I've got a few that I love (music and mostly the acting): Newsies, Cinderella, Mary Poppins, Sweeney Todd, Violet, Shrek, The Lion King, A Chorus Line, Wicked, Nine (weird, but Unusual Way really speaks to me), Legally Blonde. We've done operas in university, but I think musicals is where my heart lies when it comes to merging music and acting.
I might catch A Streetcar Named Desire in May with Gillian Anderson in it. I think it'd be good.