It depends on how crappy the competition was. Holmes didn't beat anybody on the level of Frazier, and neither did Lewis, but they beat everybody out there who they could have possibly faced. They faced very good competition, but there was no real HoF around to give them a career defining fight. It's not like Holmes or Lewis was Sven Ottke. Holmes did beat Norton, too, but of course it was an older version. I'm not convinced Foreman would have beaten Lewis or Holmes, and Foreman fell apart mentally after the loss, and to me, that works against him.

Actually, I think it's often an impossible comparison. It's two different types of greatness - absolute peak ability and performance vs resume. Here's an example. Riddick Bowe at his absolute peak (Holyfield 1) was truly great. Fighting like he did that night, he could have given Ali a run for his money, then he sparked two pretty good fighters (Dokes and Ferguson) in a total of 3 rounds. For a 9 month period, he was about as good as any HW has ever been. Then he lost it.