In my opinion there is only one who is the greatest: Muhammad Ali!
He won the Olympics.
He became the world champion.
The championship was taken away from him because of his race and religious faith.
He won his combat against racism.
And he came back, and won the world championship again.
He did many other things as an athlete, but he did even a lot for the society.
He was truly a "dancing butterfly, who stung as a bee".
Muhammad Ali is the greatest