#1 Epcot: I have always loved this park. It might be because there is so much to see and do there. It is a large park, though, so maybe you would want to do Future World one day in the morning, then World Showcase late afternoon to night (you can see Illuminations then!!

).
#2 Disney Studios: I love RRC. It is a fantastic ride, along with ToT which is another "Disney Magic" ride that is just teeming with the best of Imagineering. Star Tours is great too. You could easily do this park in one day.
#3 Magic Kingdom: This is the definitive Disney theme park, aside from
Disneyland itself. For some reason, though, this park was never my favorite. It is do-able in a day, but you would have to skip a few things.
#4 Animal Kingdom: Too out of the way for me, not enough good rides (although I have not been on EE yet, so I might have to bite my tongue for now). The theming here is great though. This is another park that you can do in a day.
But, they are all Disney and the 'World' would not be complete without them, so they are all great in my book.