In order...
1. Animal Kingdom - There's just not enough here to justify one day's admissions, and I doubt it attracts many non-Park Hoppers. As someone else said, it's a wonderful idea and what they do have is really grade-A (except the whole carnival concept in Dinoland). They just need MORE, and quite a bit more. Beastly Kingdom would take it where it needs to be. Everyone, even the casual visitor, gets that it's just too empty and not worth a full day's admissions (evident even by its operating hours!). For its size, there should be as much there as MGM, at least, if not Epcot or Magic Kingdom. I know, that takes time, but I think they could be making faster progress. It has picked up a little recently.
2. MGM - Great park, but with the loss of the actualy backlot and the lack of anything new for awhile, it's gotten a little slow there. Two or three more attractions and a refresher for some of the more dated aspects of the park and we'd be back in tip-top shape!
3. Epcot - There's already a lot here, but it seems a bit frazzled. The theming at Epcot needs to be more tighly applied around the whole park so as to give it a distinct feel again. It seems to slowly lose that with time. Innoventions needs to change in some way, shape, or form. One more addition like Mission: Space and a general concept boost and they'd be on their way. Also, some of the buildings just have an older feeling to them. Does anyone else agree?
4. Magic Kingdom - It's in the best shape of all 4 parks, imo, and not too bad off, ESPECIALLY when the Tomorrowland classics are open. The most lacking area is ToonTown, which needs something done to it. Other than that, I think it's good for now. Sure, we could always use a few new rides and a few updates- and those will come- but MK has gotten a lot of attention in the last few years and I'd like to see the other parks receive some of that now. MK is still the park that occupies the biggest chunk of my time!
-Aaron