Depending on what type of meal you are looking for, I have a couple of different favorites.
If you want a sit-down, get waited on meal, we have always enjoyed Liberty Tree Tavern in Frontierland.
If you want a buffet, Crystal Palace right on the hub as you are heading towards Adventureland is very good.
If you want a light meal - hot dogs and fries for example - we really enjoy Casey's. The ice cream across the street from Casey's makes for a great "dessert". Casey's is on Main Street, on the left corner as you are facing the Castle.