Hakeem is the one that is underrated. He should legitimately be right up there with Wilt, Bill, and Kareem, but is never thought of as on their level. Hakeem is one of the few 5 skill players the league has ever seen. I mean he is still 1st all time in blocks, 9th all time in steals, 13th all time in points, and 14th all time in rebounds (and I'm aware steals and blocks are newer and thus guys like Bill and Wilt aren't represented whereas they would be). He wasn't as good a passer as some other centers, but still had 4 straight seasons of 3.5 or more apg and a couple of others at 3 or better. His low post skills were otherworldly. He was unguardable and at the same time was the best defensive big man since Bill. He won multiple DPOY and an MVP, along with the 2 Finals MVP's. He also anchored the worst title team in league history. Aside from him, that team was downright awful.
Hakeem is legitimately a top 10 player in league history. Robinson just wasn't at that level. Frankly, I don't even know if Robinson was ever the best center in the game in any season (I haven't looked there may have been a season or two between Hakeem and Shaq that Robinson had that mantle, but it was short lived).