Jordan is the greatest athlete.
If the criteria is greatest "athlete" then I disagree with Jordan. He tried baseball and failed. If you're looking for someone who is a great athlete then someone like Bo Jackson should be mentioned since he was great for a short time in football as well as baseball. I'm not suggesting Bo Jackson should be on the list because I don't think he would get a vote and people would just laugh. But his all-around athleticism can't be denied.
Jordan deserves a vote because he was the greatest in his sport. Like Gretzky in hockey and Ruth in baseball. Ali was the greatest culturally like Capo pointed out.
I think it's easier to pick sports figures and music entertainers because there is no arguing the impact they had on their sport/culture.
I think if this poll were done on a non-Godfather and Scarface related board the results would have been different for the actor category. I believe it's hard to argue that any actor made such an impact on the movie industry to completely change the way all other actors act from that point on.