He had a fine career, agreed. But he never beat an elite heavyweight -- and he fought many. Keeping him down wasn't easy, man had great heart, but he was down more than 15 times from the day he first won the heavyweight title until the end of his career. Even Rademacher, an amateur, put him down. As for a six-year reign, no. He won the (vacant) title in 1956 and lost it to Ingo in '59. He won it back in 1960 and lost it in '62. You don't count the time where the guy who knocked you out has the title as part of your reign. And Ingo doesn't rate as an elite heavyweight in any way. Take away the Patterson win and I doubt anyone would remember him at all. He ruined Machen? He continued on quite well after that and was a longtime contender for years after that -- look it up. Patterson was well protected during his championship days -- Rademacher, Brian London, an undefeated Roy Harris (whose only notable win was over a light heavyweight, Willie Pastrano), Tom McNeely (who had NO notable wins on his ledger, and who solidified his credentials by losing three of his next four fights) ... until he fought Liston there's just nothing on his heavyweight resume to measure him by when trying to rate Patterson against elite big men. If you think he beats elite heavyweights, that's OK. I just don't see anything in Floyd's resume to justify it.
For my money a great fighter from the D'Amato mould. Better than Jose Torres, but not as good as Tyson.