This is such an ill informed opinion. People that say Jim Brown are really quite ignorant of the truth.
Take 1958. He led the league in rushing by quite a bit, but he led the league in carries by an absurd amount. He had more than twice as many carries as the guy that finished 3rd in rush yards that year.
More importantly, and we have to be real here, that season he was basically the ONLY black running back. Everyone else at the top of the leaderboard was a white guy. Come on guys.
He was absolutely dominant against the people he was playing against, but to consider him the best all time is to just completely ignore the conditions he played in.