Depending on your mood at the time, our recommended sit-down restaurants in MGM are 50's Prime Time and Brown Derby. 50's needs to be visited with a good sense of humor, because the CMs are role-playing during the meal.
Brown Derby is based on the original in L.A., and is very nice. The food is great (IMHO), and if the server is 'on', a better meal in MGM is hard to find.
We just did 'Sci-Fi Dine In" this last trip, and it was a hoot!! Imagine going to a drive-in movie theater and having your meal in the car!! Cute....
In Epcot, we bounce between Le Cellier, Rose & Crown and Teppanyaki, depending on what we want to have. Restaurant Marrakesh is good too, as is Restaurant Akershus. I got burned at Alfredo's in Italy more times than I want to admit- so we don't do that anymore. The Coral Reef restaurant in Future World is really good too!!
In Animal Kingdom, Tusker House gets our vote. It has a good variety, and although not a FS restaurant- it has plenty of variety. The only FS restaurant in Animal Kingdom is the Character Meal (a buffet) and Rainforest Cafe at the entrance.
Also, we're both doing Atkins- and all of the restaurants have been most helpful about altering foods for us. We also share entrees quite often (due to the amount of food served) and have had no problems with that either.
Good luck, and I hope that some of this helps.........