Sure. But you can never be sure if or how they would adapt to the longer distance. Some would adapt and some would be spectacular flops.
I think you are right, and for this reason and this reason alone, I am confident in picking Ali. He just found a way and adapted. I think his speed in his prime is capable of giving him real dominance in the early rounds and he can build up enough of a lead and wear his opponents down, so that he stops them in the later rounds. He trained well enough for any era and would be one of the best wrestlers in any era. As pick no 2, i say Mike Tyson. A clean and pure puncher who was always going to rip through any ranks. He was taken the distance, but none of these fighters were ever doing anything but dodging bullets to get there. In the era of smaller fighters, while he was fast enough to land and score KOs of John L sullivan proportions. He would always be derailed quickly, but he was also always going to dominate. As pick no 3, Obviously Louis is near impossible to go against. Though i wonder maybe if he is too small for the current era. That is the only risk, i think.
i doubt seriously , that any old fighter might take the shots from foreman with small gloves and much less without gloves during more of 5 rounds, the stamina is a factor when you fight during long time. if you are knock out in 2-5 no. (i hope that you do not tell me that foreman would fail always) the people here forget that tyson did not have much better stamina than foreman, if foreman was not the same in 8 rounds , tyson was not the same in 9-10. in my opinion louis is a bit overrated. i think that foreman himself would ko louis, basing on the chin of louis, basing on foreman did cut the ring very well ,basing on louis was very static and basing on the power,the aggression ,the solid chin of george during the first 6 rounds. i do not think that louis might contain to prime tyson or a prime frazier either.
There is bo fighter so big, so hard, or so tough, that sombody dosn't take him the distance. If the distace is then stretched to 20-25-45 rounds, then you have an endurance contest. Quick knockouts are basicaly a result of the introduction of boxing gloves, and Queensbury rules. In the bareknuckle era it was almost impossible to score a quick knockout. They just never happened.
Joe Frazier! He can go any distance, they'd have to keep up with him. He could hook to shreds any old timer trying to grapple him. His relentless pitbull pressure is the style to fight any roided up 6"6 modern fighter. He has the work ethic, grit, heart and determination to hold his own in any depression era, rough times, race-bias times. George Foreman did get him good, but i honestly think that George was his only kryptonite. I don't think it was a style thing, where any big bomber would destroy him. The Joe Frazier that was dodging and clowning Ali in the first fight, that defeated Ali outright, is the most versatile Heavyweight of All Times!