Well, I'm gonna vote for both Skidaway Island State Park AAAANNDD Savannah South KOA, in Richmond Hill! :B
--If what you're looking for is something easy on/off I-95, that has a pool for the kids, a lake with canoes and swans (!), FHU, level sites, WiFi, laundry, a little store, and a doggy play area, Savannah South might be the place for you. There are several good restaurants down the road that you might like, too.
---If what you are looking for is lots of huge water oaks dripping with Spanish moss, hiking trails, large W/E sites, quiet and lovely, then Skidaway is your park. It's a little off the beaten path, but not hard to get to. They have put in sewer at 16-17 sites only and it's hard as heck to get into one unless you reserve a few weeks or months in advance. (I actually just got the last FHU site for a one week stay in early March. Yay!)
I have stayed in both parks and I like them equally well. Each one has it's place, IMO. Both are clean and well-kept parks.