We often lunched at Liberty Tree Tavern, food was good, not a buffet, and it fit our MK touring plan after morning in Adventureland/Frontierland.
50's Prime Time Cafe used to be our favorite, but we found portion size, quality, and CM interaction steadily declining.
Some places have similar menus but cheaper prices for lunch. We would always visit Le Cellier for lunch, because it was same menu but cheaper and easier to get an ADR, but I think now the prices are the same for lunch and dinner.