JUST on the basis of dominance. Forget how good you think their opponents were on film, or how much of a reputation their opponents made for themselves.
Now, by dominance, do you mean winning easily/convincingly, or just consistently winning against the best?
Very interesting question. It would take a while to rank them all. How about just a few long reigns and/or lots of title fights: Muhammad Ali, Joe Louis, Larry Holmes, Lennox Lewis, Jack Johnson Bob Foster, Michael Spinks, Archie Moore, Roy Jones Jr. Carlos Monzon, Marvin Hagler, Bernard Hopkins Jose Napoles, Ray Robinson, Henry Armstrong, Kid Gavilin, Emile Griffith Roberto Duran, Benny Leonard, Carlos Ortiz, Ike Williams Willie Pep, Salvador Sanchez, Sandy Saddler More later. I got to get to bed.
I'm sure there are ten guys in every weight class who fought once, knocked their opponent out in one round, and then never fought again. They win.
They did not do it against ranked opposition, though--a different thing from our subjective judgments of fighters on film. Some of Bowe's wins were not "dominant" because they were against fighters unrecognized by any sanctioning body or Ring Magazine.
Let me give you a "for instance": Marciano's opposition is considered much worse than Ali's, even though both were facing top-ranked fighters. Norton is considered better than LaStarza, even though both were ranked in similar positions during their periods. I'm asking you to eliminate the judgment of opponents from the equation in everything but their ranking at the time. The sole question is how many of the upper echelon of the division were defeated.