It’s tough to pick just one, so I’ll go with one per park:
MK: Columbia Harbour House. Been going there since the days when the clam chowder was served in sourdough bread bowls. Sadly, those days are long past, but a combo of the lobster roll and clam chowder is one of the things I look forward to every trip.
Epcot: Tangierine Cafe. One of my first food stops in Epcot every trip. The lamb and beef shawarma platter is a go to comfort food and works surprisingly well as a pre-marathon dinner. Honorable mention to Cantina de San Angel and its fish tacos.
AK: Flame Tree Barbecue. Love the ribs and the peaceful, picturesque seating area. Be careful, though, the birds will steal your food in a heartbeat if you turn your back. Honorable mention to Satuli Canteen, which is climbing the list and may well have better food, but can’t compete with the nostalgia and setting of Flame Tree just yet.
DHS: Nothing. I’ll go out of my way to avoid being in the park at counter service time. Nothing stands out or appeals to me, particularly.