Show me any piece of logic that says it's not Fedor. He's only lost one fight on an illegal elbow, early in his career. He's run through all kinds of champions and legends.. Goodrich, Coleman, Nogueira, Herring, Kro Cop, Arlovski, Sylvia, Fujita, etc. I just hope he gets in one or two more big time fights before he gets too old so people stop doubting it. He's gotta fight Lesnar... that fight is as likely to happen as Merriweather / Pacquioa
Also I'm surprised nobody mentioned Wanderlei Silva. Back in his pride days I think he was the best pound for pound fighter of all time. I would love to see Wanderlei in his prime verse Anderson Silva now... that would be an interesting match up.
Pound for pound might be (as much as I hate him) Anderson Silva right now.. the guy's a prick but he's got so much talent its ridiculous. Too bad he's wasting it by fighting not to lose and showboating