This is actually a bit of a myth. There's no way he could've stayed at welterweight, I imagine he'd have loved to because it's where he'd have gotten a rematch with Barbados Joe Walcott - but he just grew out of it. He was a middleweight by twenty one, and a light-heavyweight by 28. His progression up the ranks is a result of fighting at the highest level from a very young age and an impoverished background, and a very unique, top heavy physique. He'd have always filled out to be around 180 IMO, as that was what I'd call, his natural weight. Still, though. A highly, highly impressive fighter - my pound for pound number two.
Wlad wouldn't even be considered for best résumé, IMO. He's a great fighter and categorically top ten - but it's his long title run that got him there, not because he beat some Murderer's Row. Everybody should have Ali at number one. Liston, Foreman and Frazier are some of the best heavyweights of all-time and they would be almost anybody else's best win. Ali has five wins over the three of them - so yeah, he's defo number one based on that alone. There's no need to go into the 30 something ranked fighters he beat. Holyfield in terms of who he beat has to be up there, but sadly, they were past their best. Still quality, mind you. But past their best, nonetheless. I'd probably have him second, still but I have no objections to him being below Lewis, Louis or Holmes. Lewis has some brilliant wins on there. A still brilliant Holyfield and a prime Vitali. Some mid-tier guys like Rahman, Mercer, Tua, Bruno, Rudduck, etc; and then the super fight with Mike - which doesn't look too impressive in hindsight, but we do have to remember that Mike was given a very good chance in that one. I have a slight feeling he was a bit better than often made out to be, for that one. The subsequent losses possibly being chalked down to even worse training habits. Louis would be my four. Wins over guys at varying points of their primes throughout the thirtees, slaughtered the division in the 40s and even went on to beat five ranked fighters in the fifties - while as shot as you can be. Walcott, Schmeling, Baer, Carnera, etc; are all top wins IMO. When I did a count, comparing Ali and Louis' record vs top ten ranked fighters, Louis was 38-3. That's insane. Especially given that Fury today, is like 2-0-1, and Joshua is like 4-0. I'd have Holmes at five, although that could just be because I rate the 80s pretty highly. Norton, Witherspoon, Smith, Mercer, Berbick, Shavers, Williams, etc; is highly impressive to me, but I can see him being removed on the same basis that I wouldn't have Wlad. #05. Larry Holmes #04. Joe Louis #03. Lennox Lewis #02. Evander Holyfield #01. Muhammad Ali
Oh and honourable mention to one of my personal favourite heavyweights. Johnny Risko. Guy was a high performing gatekeeper who probably has the best win sheet in the whole of the 30s.