Welcome to the site!
I used to live in Atlanta and, sadly, I couldn't find much in terms of retro gaming. There are a few Play N' Trades scattered throughout the OTP area. One is in Tucker, one is near the Green Hills (?) mall, and I think there is one more somewhere. Maybe Cumberland? It's been a while since all of them have been disappointing. The only good one is in Woodstock, but that's a hike.
There is also a place called J2 Games which is in Buford, but they have really dumb hours. At least, they did the last time I checked. If memory serves, they're closed on Sundays. You know...the day when people actually are free from the 9 to 5 and can go shop? There prices are very high, but they have some good stuff.
There's a small store near Hiram called Gator Games. I wasn't impressed and the customer service was crappy.
One of the Play N' Trades turned into an independent store. I think it's called Wizardry Games? Something like that; it's near Gainesville.
Atlanta has a ton of pawn shops, so if you're ever around Norcross or Lawrenceville, you'll likely find them. Whether or not they have games is an entirely different matter.
That's about all I can remember off the top of my head. Happy hunting and welcome to the site!