All worth doing at least once:
Six Flags (and Whitewater if you're into water parks)
Georgia Aquarium
Braves game at Turner Field
World of Coke
Laser light show at Stone Mountain
Eat at the revolving restaurant Sun Dial on top of the Westin Peachtree
See a concert at The Tabernacle
Eat at the Flying Biscuit
CNN tour
Check out Piedmont Park (especially if they're still doing the free outdoor concerts...I think that's Piedmont...)
Dinner and local bands at Virginia Highlands
Eat a burger at the original Vortex in Little Five Points (and check out Junkman's Daughter while you're there - everyone has to once; and the AWESOME Criminal Records local music store)
Do a weekend on the Chattahoochee (canoe, kayak, raft, etc.)
Zoo Atlanta
I've got plenty more food recommendations up my sleeve. Just ask me.
lyte, I don't think you're getting all you can out of Atlanta. Maybe you just need to NOT live there to appreciate it.