In general Disney food in Walt Disney World is fantastic though pricey. There are a ton of sit-down places with excellent food, and the World Showcase has a lot of great counter service places (esp. Morocco). At their hotels they have some world class restaurants like Victoria and Alberts, California Grill, Jiko (and also next door Boma, which is a favorite of mine).
Food in Disneyland can be good, but it's more hit and miss. While some of the counter service fare is so-so, the Blue Bayou is great, and there's a lot of excellent food in Downtown Disney and in the hotels on property. I ate at a place I can't remember the name of in the Grand Californian that was superb.
Never been to Disney Tokyo, but I heard the food there was excellent.