Looks like I'll be in the minority (I really am one of the only people I've seen with this opinion), but I'm going to say Animal Kingdom. With Avatar Land, it now has not only a well balanced, solid collection of rides, but it has the best theming of any of the parks in Florida. It also has fantastic animal exhibits and shows to where your entire day can easily be filled up. Plus, the park is amazing at night.
Islands of Adventure is a really solid park (third best in the state I'd say), but it has far too many weakly themed areas to be the best for me. Toon Lagoon and Marvel Island look too "plastic-y" for my liking. Then again, it's just my personal opinion, and most screen-based rides rarely do much for me. While there are exceptional examples (Flight of Passage, Spidey, Harry Potter FJ, etc.), it puts Universal at a disadvantage for me.