At MK we like Columbia Harbour House. Their Cap'n Special (fish, chicken, fries or carrots) and their salad are excellent. I also like Casey's. I love sitting right outside eating my hot dog or corn dog nuggets, listening to the piano player, and gazing at the castle. They're very cheap also. Their hot dogs are big and only like $3.79 or so.
At AK Tusker House has excellent salmon and Flame Tree has large portions of BBQ that's good. My GD loved their corn on the cob. The tables along the river makes for a cool and peaceful meal.
At Epcot I'd go hands down for Tangierine Cafe in Morroco. Loved their Swarma platter, although the fish and chips in England are also pretty good. At Epcot you may just want to snack your way around the world: churro and margarita in Mexico, school bread in Norway, German chocolate cookie in Germany, fried wontons in a bag in China, cannoli in Italy, funnel cake in America, Kaki Ghori in Japan, Swarma sandwich in Morroco, Marvelous in France, Fish & Chips in England, maple candy in Canada. Did I leave any countries out?
At MGM--hmm good one, none of their CS are particularly appealing. I think I'd take the boat over to the Beach Club and eat at Beaches & Cream (just to get a No Way Jose Sundae, if nothing else).
DTD-Earl of Sandwich-cheap, but very good