Outkast was the first act (artist or group) from Atlanta that was more than a one hit wonder. The Dungeon Family sound had several musical influences, but they modernized and pushed that sound forward. The legacy of being the unit that brought national attention to Atlanta hip hop is nothing to sneeze at...
Southernplayalisticadillacmuzik is definitely not they best album, who thinks that? It was a strong intro but the real gift is how they diversified they creativity in subsequent albums. From sound to subject matter, you can name a group or two that had a similar "essence" but then Big and Dre were actual lyricists too, and no other comparable style had that in one package. They were 20 years ahead of their time with a style that would look ordinary in 2015 but stood out in 1995, where part of the intrigue was their weirdness...
I'm also inclined to say if you don't think they are GOATs, your ear either needs checking or you aren't familiar with they catalog. There really is no debate that they on the GOAT list, the debate is normally centered on "where". Its unquestionable that they Top 5, and to me, they Top 2. They have a case against any other group ever, excluding nobody...
Nas has always been a little overrated. Illmatic is a classic but Nas should have more classics for the body of work he has. Illmatic not the only one of course, but people get caught in this "man he can spit" thing without properly assessing the other Mark's of greatness about an artist, they've been overeating him since the 90s...
Nas is a GOAT though, but he not nearly as high as people want him to be...
Yeah, ATL definitely had it's one hit wonders, but I'd say Arrested Development and Kriss Kross were more than one hit wonders. They just weren't acts that were looked at seriously or as ATL artists. It's one of those deals where you had to read a press release or article or word of mouth to know where they were from. Kast made it obvious from the jump.
With Nas, I think he deserves every bit of the GOAT accolades he gets. My whole point with him is, I was making the case that no one comes out the gate as a GOAT. GOAT status is something that is assessed over time.