I definately think this will vary from person to person, but I'll list all my favorite rides.
Animal Kingdom: Kali River Rapids, Kilimanjaro Safaris, Dinosaur, Primeval Whirl, It's Tough to be a Bug, and Festival of the Lion King (I haven't been since they opened Expedition Everest)
Disney Studios: Rock'n'Roller Coaster, Indiana Jones, The Great Movie Ride, Muppet Vision 3D, Backlot Tour, and Star Tours (again, I haven't been since they opened Lights, Motors, Action)
Epcot: Spaceship Earth, Universe of Energy, Living with the Land, Mission: Space, Test Track, Honey I Shrunk the Audience, Maelstrom, and The American Adventure (and again, I haven't been since they opened Soarin)
Magic Kingdom: Jungle Cruise, Pirates of the Caribbean, Splash Mountain, Big Thunder Mountain Railroad, Haunted Mansion, Peter Pan's Flight, Space Mountain, Buzz Lightyear's Space Ranger Spin, Tomorrowland Transit Authority, Mickey's Philharmagic, and It's a Small World
That's all I can think of right now.