I didn't care much for Carousel, but now, I "like" it.
Same for Ragtime, except I LOVE it! I listen to most of the songs at least once a day.
The Lion King. I thought it was going to be great, but after I saw the show, I came out thinking I had just wasted 2 3/4 hours of my life.
Les Miserables didn't really excite me much, and I had only listened to few of the songs (OBC) when I was taking a bath (just a background music, I guess. I didn't listen to it carefully), but I didn't really like it. After I watched the 10th Anniversary DVD, I just fell in love with every single song. Same with Miss Saigon.
I didn't particularly have any feeling for Sweeney Todd, but now, after watching Hearn/Lansbury DVD, I fell in love!
I somehow hated Chicago (original) after seeing Tony Awards clip on Broadway's Lost Treasures, but after watching the movie, I fell in love with all of the songs!
It takes me quite a bit of listening for me to start liking any musical, unless it's flat-out comedy like Avenue Q.
"Hey, you! You're the worst thing to happen to musical theatre since Andrew Lloyd Webber!"
-Family Guy