As an Atlanta native who is something of an aquarium junkie, I am a bit perplexed by the 2 negative reviews I read here: one person thought there were no "exotic" creatures here, and another claimed that "it wasn't truly the largest." I don't know what aquarium you folks went to, but the Georgia Aquarium in Atlanta is without question the the largest on the planet - whether you use a yardstick that measures square feet (more than the Georgia Dome) or by how much water is in the exhibits - more than 8 million gallons.
As for exotic and unusual specimens, as of this writing there are currently four whale sharks and four manta rays in a single humongous tank that they share with several species of sharks: hammerhead, sand tiger, blacktip reef, and a few other very unusual species. There are no other facilities in North America, and probably not any in the western hemisphere where you can see whale sharks and manta rays. I have an annual pass - have been there many times, and can still spend hours being awed by the majesty of the whale sharks and mantas. If you aren't impressed by these, perhaps there isn't anything in the ocean that will make you go "WOW!"
I've visited many top-rated aquariums including the big ones in Baltimore, Monterrey Bay, Chicago, Boston, Tampa, and Singapore - and while I will tell you they all are great, I personally get a bigger "WOW" out of sitting in front of the huge glass wall at the Georgia Aquarium and watching the whale sharks and mantas (and all the rest) go gliding by. It's SO big - if you know how an IMAX screen completely fills your field of view so that you feel immersed in the experience - then you begin to have an idea of what it feels like sitting in front of the giant viewing area at the Georgia Aquarium and watch a rare 25 foot long whale shark swim past you.
Just my personal opinion...