Our favorites:
Alfredo's, Rose and Crown, Le Cellier (not any for the buget-concious)
Bomas was wonderful!
The Kona Cafe for breakfast (Tonga toast is a MUST)!!
If you're doing 50's diner, be hungry...it is a TON of good ol' fashion cooking! My sister-in-law hates 50's as she says she wants to relax and enjoy her food and doesn't want anyone hassling her while she eats and deals with her kids...you HAVE to be in the right frame of mind for that place, but it's a kick if you are.....if you don't have a sense of humor, stay away!!
We also love Beaches n' Cream, the fish and chips in England (Epcot), and ham and cheese sandwiches in the French pastry shop in Epcot...Whispering Canyon is fun for breakfast, but we weren't crazy about the dinner...
I agree it's better to visit SciFi for a snack only....WAY too expensive and only so-so food that you could pick up in any of the snack bars in the parks...
Not a fan of Rainforest, but they have them in other cities...
That's it off the top of my head...
Go and have fun!!!