I've now been to 6 Off Road Parks - here is my ranking on a scale of 1-10.
Rankings based on riding only, not facilities, price or service.
Highland Park ( Cedartown, GA) ....................................... 10
Durhamtown Plantation (Union Point, GA) ......................... 8
Carolina Adventure World (Winnsboro, SC) ...................... 7
Brimstone Recreation (Huntsville, TN) ............................. 5
Whissenhunt Trail System (Oconee Natnl Forest, GA*) ....... 5
Croom Motorcycle Area (Brooksville, FL*) .......................... 2
* Publicly owned and operated
It's somewhat subjective depending on whether you like well groomed or less groomed trails and your riding level. I'm a low intermediate rider and like both kinds of trails.
Highland Park, Durhamtown and Carolina Adventure World are reviewed in more detail in the off topic section.