Usually you'd go prime for prime. They'd be close enough in weight and dimensions for comparison. And tbh if you have to make the match up against the end of Alis career you're basically stating how competitive Usyk would be. This is coming from someone who typically isn't a fan of cross era match ups.
To be honest, I usually stay out of these cross era match up threads myself. A difficulty in the Ali-Usyk match up is the age gap. Ali at 25 was undoubtedly faster than Usyk at 37. But then Usyk at 25 was undoubtedly faster than Usyk at 37. The Usyk that beat Fury is well past his physical prime. He's a little bit like Bernard Hopkins toward the end of his career. Winning more with guile and smarts than physicality. Nobody's reflexes and feet are better at 37 than 27. It's a matter of what a guy has left and if he's able to compensate for some amount of physical decline with accumulated smarts and experience.
These are all just opinions. You have yours and I have mine. There is no way to prove any of these fantasy match ups so there's no sense getting emotional over it. Ali, in the second half of his career was given some gift decisions and was a shadow of his former self. He was a very beatable guy. Ali was taller and faster than most HWs he fought in the 60s. He would not have that size advantage on Usyk. Ali was indeed the fastest HW arround in the 60s. But sometimes timing beats speed and Usyk has great timing. The Usyk you are watch fighting at 37 is undoubtedly slower than Usyk at 23. The speed argument is overrated in my opinion. There is no question in my mind that Usyk at 37 beats Ali at 37.
I haven't seen film of Usyk at 25 to be able to do a good job of that. Probably hardly anyone here has.
It’s not just about speed because Ali had excellent timing as well plus the intangibles such as ring generalship, mentality etc. Usyk is great Ali is the greatest an opinion Usyk himself shares. Stylistically Usyk would struggle against Smoking Joe Fraizer.
Everybody defers to Ali and pays him respect as much for what he did outside the ring as in it. The doesn't mean they wouldn't have a chance against him in the ring.
I am not deferring I am judging by his ring exploits. He fought a literal murderers row of opponents who were highly skilled. This generation are not as well schooled. Put Ali in this generation and it would be like child’s play. Usyk really a Cruiserweight is beating these guys due to the disparity in skill sets, fitness and IQ.
Boxing is the only sport where we think the athletes get worse over time. Boxing back in the day was on network TV. It was free for anyone to watch. Because of this I think the sport was more popular. A lot of people watched. I did. There was no alphabet soup of organizations or only the beginning of it. Most people knew who the champs were, and who were the contenders. The fighters had broad name recognition so we think they were a murders row. When I was a kid, there were plenty of old heads around who thought Joe Louis would have walked over Ali. Some really old heads who thought Dempsey was the greatest. Boxing is a sport where we over romanticize the fighters of the past. It's tough to compare eras but in general, athletes in all sports get a little better over time.
His in ring achievements are outstanding though he beat 30 ranked Heavyweights beat 2 Heavyweights who are amongst the top 10 Heavyweights of all time Frazier, Foreman, then you have wins over the likes of Liston, Patterson, who would be top 20 Heavyweights of all time. His peak during 1964-1967 he beat 7 ranked Heavyweights won 9 world title fights and had 7 stoppages in those 9 world title fights. If any Heavyweight now including Usyk had statistics like that now everyone would be ranting and raving how good they are.
You can't tell me Fury's love handles and Zhang throwing only 200 punches over 12 round is peak athletic performance. A 47 year old Foreman was throwing up to 400+ punches. Bigger doesn't mean better Usyk has shown that and he's the size of Heavyweights from 30 or 40 years ago and his toughest fight was against a Cruiserweight not a giant lumbering Heavyweight. Infact I think the Heavyweights have got worse they're too big they don't have the cardio/stamina and as Lewis said you don't see the fluency of Heavyweights throwing combinations anymore. Name me a Heavyweight now outside of Usyk who looks more impressive than a peak Lewis, peak Ali, peak Holmes, peak Tyson, people like to say the sport has evolved but I'm not seeing evidence of it certainly not in the Heavyweight division.
I don’t I have watched different eras. Ali and Usyk have the same dimensions. I know Ali at his best and Fury at his best Ali stops him.
No way Usyk can have statistics like that. It's a different era. Usyk stayed at cruiser too long. Fighters fight less frequently, ... Going by statistics it's not close.
In your imagination it is that way. In my imagination, John J Magilacutty who fought three hundred bouts in the 1880s beats them all. Prove me wrong. You can't. It's all conjecture and opinion. In reality, we will never know because we don't have a time machine.