Oh no! This is going to be a tough one for me. We have had so many great dining experiences at Disney World that I have LOTS of favorites. Ok, I'll TRY to narrow it down but there's no way I can pick one so forgive me
Yachtsman Steakhouse - We had the best meal there on our first trip to Disney. I was happy the moment we walked through the lobby of the YC. I know some think it is a bit stuffy but I just love the decor and the hardwood floors. We had the earliest p.s. that is possible since we did have our children with us. We practically had the restaurant to ourselves, sat by a window so we had a pleasant view as the sun started to go down. The staff from server to maitre d' and manager all came to the table and talked with us and complimented us on how well behaved our children were. Everything was wonderful. The salad, the bread they served, one being an onion bread of some sort was still hot when they brought it to the table. I know my cholesterol level may pay for it one day but I am a meat and potatoes girl at heart. I ordered the prime rib and it was done exactly how I liked, and it melted in my mouth. My dd was 7 then and she is now nor ever has been a red meat eater. I had her try a bit of my prime rib and it's good thing it was a nice sized piece since she kept asking for more bites since it was so good. DH loved his steak and all 3 kids enjoyed their meals and coloring so much they were angels (that always helps a dining experience doesn't it parents? LOL)
Liberty Tree Tavern - Only have done lunch there but love it. Their Sally Lunn rolls are great (can you tell I'm a bread lover too?) The food is good, not stella , but the atmosphere I just love. I could LIVE in Liberty Square.
Le Cellier - Yup the meat, potatoes, and bread thing again

We have had great service there, I adore the pretzel bread, prefer the filet to the prime rib, and like the atmosphere. It seems cozy to me.
For fast food:
Beaches 'n Cream-It's a tradition and there is just something about those burgers and fries that we love.
Cantina in Mexico - I have to have my Tex-Mex fix once in a while and enjoy the taco salads and sitting by the water looking over at the other countries.
Ok, you know I could go on but I've made this post long enough. Sorry, I tend to ramble when I talk about Disney <sigh>.