I agree that it's because of the way the Seas tank was designed with the central viewing area. That seems good in theory, but in reality it's too easy to see the walls and realize it's just a tank. And yes, the Georgia Aquarium also has one of those glass tube walkways through the center of the main tank.
I think the issue for visiting the Georgia Aquarium is that Atlanta isn't really a tourist city. The Aquarium is a great attraction, but there's not a ton else here to do for visitors. The Center for Civil and Human Rights that's right next to the Aquarium is very good and I would recommend it to anyone (they're building an expansion there right now), but the College Football Hall of Fame is not especially good even if you care about college football (and I do). The World of Coke is basically nothing. The Atlanta Zoo does have giant pandas which is a rarity, but the National Zoo in DC also has them and there's obviously far more to see/do there. The rest of the zoo is small and not special, although I'm a bit spoiled by growing up 30 minutes from the NC Zoo which is one of the largest in the world.
The only other thing I can think of is the MLK Historic Site, which is worth visiting, but there's really not a ton there.