I think Ken Norton gets very underrated due to being in the greatest HW era there has been. He just met a beast against Foreman and in his prime only really lost debatable decisions to Ali and Holmes, as well as beating Ali once. However, I feel that due to his less than aesthetically pleasing style and being overshadowed by the magneticism of Ali and Frazier and the raw power and fear generated by Foreman that he gets overlooked. He also was coming out of his prime by the time he fought Holmes so didn't really have a chance to dominate a weaker division, but was more the 4th guy when the division was great.