I like Burger Digs in JP (counter) and also Captain America Diner MSHI(counter).
If you want to eat outside the park I reccommend Jimmy Buffet's for casual dining and Emeril's if you want to go all the way ($ wise)
<a href="http://members.tripod.com/~dznefreek/IOAGuide1.html">Visit the Unofficial Guide to Islands of Adventure!</a>