Well I haven't eaten at ALL the restaurants yet so I can only tell you from personal experience. Keep in mind I'm a very picky eater so I tend to like the restaurants that serve food that I can pronounce. I like any sit down place that serves mac n cheese, chicken, pizza, etc.
My favorites
1. Garden Grill, the best "normal" food in the world IMO! The characters and rotating restaurant make it even better.
2. 'Ohana - honestly I didn't like much of the food. I don't like a lot of meat and I don't like grilled foods, so I ate my daughter's mac n cheese. (Everyone else at my table loved the food - they aren't picky like me) Despite me not liking the menu, the atmosphere was so incredible I will go back over and over again. We went during Wishes and it was so awesome to watch Wishes while sitting at a table eating dinner!
3. Any of the buffets - Crystal Palace, Chef Mickey's, Donald's breakfastosaurus, etc. Again, they offer normal foods so I love em!