At this point in history, I think that Kareem is probably the third best center in NBA history, behind Wilt and Russell (pick your order). Depending on what Shaq does between now and the day he hangs up his size 22s, Kareem might be pushed down to 4th best.

As for Rodman, I wouldn't list him as one of the top PFs of all time, but he was a hell of a rebounder. I did notice that when he was with Detroit, his defense was his first priority, and then later on he fell in love with rebounding and his defense took a back seat. He was never quite able to peak with those two skills at the same time.