Rating champions from different divisions is a little too 'apples and oranges' for me but the two things that immediately sprang to mind was that Wladimir is probably a more bona fide champion than his brother but I can't help but feel that Vitali allowed Wlad to be the champion that he has.

Also seeing as Joe and Darius are at similar weights - Id have say the have had very similar careers. Darius has the lineage thing but then he doesn't have Roy Jones on his record ().... Dunno... Very similar careers.

Kostya Tszyu? Pass.