I lean towards the later musicals, because, to me, there is a more fluid transition between story and number, where in the older ones, action happens and they sing about it.
What are some of your favorites?
Little Shop of Horrors
Phantom of the Opera (One of the two that I like by Andrew Lloyd Weber)
Jesus Christ, Superstar (This is the other)
What are some musicals you just plain don't like?
Grease (this combines two things I hate: High School and the 1950s)
Cats (It was nice to look at, but that's about it)