The Greatest?... there is no "Greatest Fighter" ... it's all subjective. The old timers always get the nod over newer generation fighters I feel because they fought more often (because financially they had too) and their fights were more significant because there weren't a bunch of alphabet belts, and boxing was still a mainstream American Sport. I honestly believe a lot of the old time "Great" fighters would get destroyed against some of the guys that came around within the last 30 or so years. I don't think Marciano would beat Tyson, Ali, Holmes, the Klitchko's....then again, some of the guys would dominate today's sport....Tommy Hearns would beat any welterweight out there today and so would Ray Robinson IMO....but again it's all opinion.