our favorites are easily le cellier and chefs de france. we typically do both on the same day and then return to them multiple times per trip. the french onion soup at chefs de france is my favorite soup on earth. i usually get the duck entree and finish with creme brulee. at le cellier, i always get the filet mignon. i start with beet salad if that's an option, but i also remember having a wonderful duck crepe a few years back there. all the desserts here have been a home run, including the creme brulee, chocolate "moose", and a layered smores thing. coral reef had pretty good food and we like sitting by the tanks (be prepared to wait if you want to get a table by one).
unlike the other posters, i will say that i hate sunshine seasons. no matter what i've had there, it's been pretty bad. i also really dislike mexico's QS whose name i always get confused (i think it's la cantina de san angel?). terrible guacamole and nacho toppings. to be honest, i don't think we really like most of the CS offerings in epcot. we didn't like china's or japan's either. the norway bakery has some good treats, but i don't think we've tried the sandwiches or "real" food. morocco is probably our favorite CS and has good shawarma, plus platters come with baklava. the bakery in france is a must for us for pastries and sweets.