In order from favorite to least favorite, I would say: Epcot, Magic Kingdom, MGM, Animal Kingdom. I don't dislike the animal kingdom, though, it's just that I like the other three more. But really MGM and Animal Kingdom are basically tied, I only prefer MGM by a marginal amount.
I think there are some beautiful attractions at Animal Kingdom, and I think the theming is a refreshing departure from the typical Disney magic (I'm not saying that princesses and fairy tales are a bad thing, but it's good that Disney is incorporating some non-Western traditions into their parks).
My least favorite rides: I'd say the Body pavilion (not sure what it's actually called) looks like a cheap, crappy regional science slash children's museum. Very, very disappointing. Cranium Command is OK but everything else is just awful. Everything else at Epcot, however, is spectacular.
I think Drew Carey's thing is awful at MGM.
I'd say that Carousel needs a facelift. They don't need to change anything per se, but I'd make some renovations: new seats, new curtains, new lighting, re-record the music and install a new sound system, and make the audioanimatronics a better reflection of Disney's capabilities.