Well my two favorites are the California Grill and Citricos. They're signature dining restaurants and pretty expensive. Cali Grill is more kid friendly than Citricos.
At MK:
To me, the Crystal Palace is just a must-do part of the MK. I have a lot of good memories of eating there as a child.
I like Columbia Harbour House for CS. If it's good weather, they have some outdoor tables that have a nice view of the Liberty Belle Riverboat going by. Or if it's hot, they have lots of indoor tables.
At Epcot:
Best park for food by far!
I always have such a difficult time deciding where to eat for CS meals here.
If I'm in Future World, Sunshine Seasons always wins out. In the World Showcase, I like the CS in Mexico, Morocco, and France best.
At AK:
Pizzafari has lots of indoor seating which is great when it's hot. The decor inside is adorable!
Flame Tree is good if the weathers nice - wonderful views of the park, but all the seating is outdoors.
Haven't been to HS in almost 10 years, so I can't really comment on the food there.