Lewis would outweigh Dempsey by a mile, and had that powerful right hand. He was also very smart and had an effective jab. Still, I'm thinking Dempsey would be too much for Lewis. If you watch Lewis-Tyson, you can clearly see how uncomfortable he was in the first round when Tyson came out fast. Of course, Tyson only had one good round left in him, but Dempsey would come after Lewis for several rounds, and in a much more ferocious way. Dempsey was fast, hard hitting, and had tons of heart. I see Lewis on the defensive from the start of the fight. He might even put Dempsey on the canvas with that powerful right hand of his, but Dempsey would get right back up, and keep on fighting. Dempsey would work his way under Lewis' long reach and hit him from every angle with ripping shots. With his speed, power, and determination, there would only be a matter of time before Dempsey has Lewis hurt. I see this fight ending with a brutal KO. Jack Dempsey by KO6.
Based on Dempsey being devoid of much skill and Lewis being 4 stone heavier, a bigger puncher and one of the best of all time.
Specific predictions of this kind have to be based on some sort of tangible evidence from the real world. The only occasion that we know of where Dempsey was stopped, was a fight early in his career when he was a regional level fighter, which might have been a dive. This means that we dont really know exactly what it would take to stop a prime Dempsey, much less whether it was likely to occur in a specific manner. On the other side of the equation, while Lewis would definitely be the best person that Dempsey had ever fought, I dont think that we can definitely say that he would be a harder puncher than anybody that Dempsey had fought. So in summary, your prediction is the worst kind of unsupported speculation.
Ive seen the fight with Willard and thought it was awful.the 2 fights with Tunney showed a better but slower fighter. Luis Firpo managed to put him on the deck so keeping him there would have been easy for Louis, Lewis, Holmes, Foreman, Liston, Frazier, Bowe, Tyson, Holyfield, Witherspoon etc etc
Saying Dempsey improved after Willard is nonsense. The converse is true. The thing is with Lews, he isn't just bigger than Dempsey, he's a greatly skilled fighter himself and very multi dimensional. He can jab and move, he can seek and destroy, he can frustrate and spoil he can go to war he can really do it all. I do think Dempsey is a better fighting machine p4p but not by much and not enough to overcome the weigh disparity he would be facing. Dempsey rolling a jab and landing a huge right hook left hook combo wouldn't exactly surprise anyone but Dempsey winning rounds where he doesn't score a knockdown would be a surprise in my mind. Basically I think Dempsey has a punchers chance and that's not enough for me to pick on.
It's absolutely not unfair to compare champions throughout history. If there's one thing Dempsey proved it's size doesn't beat him alone. To beat Dempsey you have to be better than him. Or of similar skill but a lot bigger. Lewis beats Dempsey but not in a mismatch.