Their catalog is too thin. In a 25+ year career what do they have, like 5 albums? That's a 1 album every 5+ years average, that's too light for any GOAT conversations. Not to mention they're too inactive. We say a 25+ career but how many of those years were they actually active? We do that too much in hip hop, give people the longevity nod just because they came out a long time ago, that don't mean they have been active all those years tho (See LL Cool J, Ice Cube, Wu Tang, countless others). Jay-z and Nas have actually been actively releasing music every 2 years or so since the early 90's, those two guys are on a whole different planet than every other rapper, IMO. They just recently started slowing down, after they were in their 40s. So yeah, Outkast discography is too light in the cakes, but they are obviously one of the most talented rap groups ever, probably the most talented.