Disneyland / Magic Kingdom
- a tie, not because they're the same, but because of the differences. Disneyland has a lot of unique little bits to it but it also has, generally, better theming (think Fantasyland). Magic Kingdom, though, has the unique feeling of being away from it all. You're out in the middle of nowhere which has a nice kind of "leave the world behind" feeling to it.
DCA - I haven't been there but with everything I see of it I really want to go. 10 years back it was a dud. Now, it looks really cool.
Animal Kingdom - it's really such a pretty park. I'm not even big on the animals but I love the way the park looks.
Epcot - needs love. I can still spend a day there but Future World needs lots of refurbishments and World Showcase is unique with the countries but it needs more countries and some more unique country-related rides. Finish the Rhine River at Germany. Add something like Australia, Spain, Brazil, Russia, etc.
Hollywood Studios - the only Disney park I've been in and, while waiting on Fast Pass times to come, wondered, "Now what am I going to do?" The only other time I remember having that feeling was at Busch Gardens Tampa around 1990. I walked in, Poked around for about 2 hours, and left. They've expanded that quite a bit (BGT). At this point I actually want to go back there but that's 25 years of apathy that they had from me (and apathy means no money coming from me). Thankfully, it looks like DHS is getting some love so, hopefully, 5+ years down the line it's a premier park.