Choosing just ONE is tough but here goes:
Breakfast:
Grand Floridian Cafe
Beautiful decor, relaxed meal. Ask for a window seat to see the GF Courtyard.
Lunch:
Hollywood Brown Derby
"Relatively" quiet meal for a theme park lunch. Also, a nice retreat if you are visiting during the summer. The darker decor is inviting when it is stuffy and hot outside.
Dinner:
California Grill
Great view, good service, yummy food.