I'll preface my recommendations by telling you that our taste for food is very much pedestrian. We regularly eat at fast food places, and chain restaurants, and avoid what is often considered "fine dining" like the plague.
Our favorites include
MK: Peco's Bill, Cosmic Rays (they offer a wide selection, and the entertainment is pretty cool) and Columbia Harbour house (I love the fish and chips)
Epcot: AVOID the Electric Umbrella! We like Sunshine Seasons, and the Yorkshire County Fish Shop.
AK: Absolutely the Flame Tree BBQ
DHS: The only counter service we've tried is the Studio Catering Company, and we enjoyed it very much.