Depends on what your situation is. The Signature restaurants are obviously the best. Those are the Flying Fish Cafe which is at the Boardwalk and the Yachtsman Steakhouse which is at the Yacht Club. I prefer the Flying Fish but you can't really go wrong with either choice.
If you want a more inexpensive option or if you're on the dining plan, an option that only charges 1 TS, then Spoodles would be your best bet which is also at the Boardwalk.