Magic Kingdom: Cosmic Ray's. I love Sonny Eclipse and their toppings bar really helps me get a lot for my money. I usually order the vegetable burger and load it up with mushrooms, onions, tomato, and lettuce. Then, to completely cancel out all of the vegetables I consume, I cover the fries in that cheese-like product that all snack bars have. Then, I grab a table where I can enjoy Sonny's music.
Epcot: Tangerine Cafe in Morocco. The food is excellent and the portions are quite large. I have no problem sharing a meal here and still getting completely filled up.
DHS: Backlot Express. Truth be told, the counter service restaurants here aren't much to write home about, but I do like Backlot Express. I love the movie props and the music and the food, while rather standard gets the job done. It's also nice to have the option of sitting inside or outside which isn't a luxury awarded you if you are dining at Studio Catering Co. or anywhere in Sunset Ranch. It's also the only counter service restaurant in DHS that offers free refills.
Animal Kingdom: Restaurantosaurs. I have fun eating here and enjoy the food. Like Cosmic Ray's, it has a toppings bar which is nice and like Backlot Express, the refills are free.
Downtown Disney: Wolfgang Puck Express. LOVE it. Excellent food and service. Make sure you do take some cash with you as this is a counter service restaurant that does have servers and many patrons tip here. Truth be told, for a counter service credit, this is possibly the very best option. The food tastes like anything but fast food and thanks to servers who will bring you your food and refill your drinks, it is a great chance to kick back off of your feet and just recharge.