Original: Frequently cited as the greatest boxer of all time , Robinson 's performances at the welterweight and middleweight divisions prompted sportswriters to create '' pound for pound '' rankings , where they compared fighters regardless of weight .
Simplified: Sugar Ray Robinson ( born Walker Smith Jr. , May 3 , 1921 -- April 12 , 1989 ) was an American boxer who won the welterweight and middleweight world championships .