Roy Jones Jr. is the greatest boxer of all time. He is leaps and bounds above Ali and anyone else in the running. In his prime he was unstoppable (except for his dq loss that he avenged). His moving up in weight to take the heavyweight title made it hard for him to regain his speed though when he went back to his natural weight which is why he lost those 3 fights. I'm not saying he's good now but shit nobody could take him in his prime he was invinsible.