Tough choice. The only ones we have not dined at are Japan and Italy. And we try Tutto next month.
I can't say that I have an Epcot favorite. If I HAD to choose it might be Chefs. But I like most any of them.
I voted for Le Cellier, but I must give snaps to Coral Reef as well! We ate their for the first time earlier this month and loved it. And I don't even eat seafood! But the steak was yum and we had great service and loved the ambiance. We'll return for sure!