I've been going to Savannah every spring for years. The 3 best restaurants are Olde Pink House, Garabaldi, and Elizabeth on 37th. Chart House is a chain but is also good. My personal favorite is Garabaldi, but Olde Pink House is similar (but without the Italian dishes) because they have the same owner. You'd be doing yourself a disservice if you didn't order the shellfish platter.
Lady & Son (Paula Dean) is overrated IMO, and Pirate House is just terrible. Vennie's Pizza at City Market is good cheap food.
http://garibaldisavannah.com/
Garibaldi's is great, but their acoustics is awful. I can't hear a damn thing in that restaurant.