I think we can all agree, if you had Tyson at his 80s peak, and Ali at his 60s peak, it'd EASILY be not only the biggest fight ever. You're talking about POSSIBLY the biggest sporting event in history. What kind of numbers would such a fight have done? I mean, assuming both are their peak of their abilities and skills and the fight happens in modern times.
These kinds of numbers comparisons are kinda pointless because you're comparing two guys who fought in an era when boxing in the US was a mainstream sport and a lot fights (especially during Ali's time) were on free TV ... If the PPV model had been invented in the 50s or something, the sport in general would have become just as marginalized by the 70s as it is today ... If people had to pay $70 to watch the Super Bowl on tv, would it get 40 million sets tuned in like it does now? Not a chance in hell... PPV has been a great money maker for a few individual fighters, promoters and cable networks but it's one of the biggest reasons the sport has nowhere near the general fan base it once did ... Compared to a Tyson or an Ali, Pacquaio and Mayweather are minor celebrities really
First instinct is to immediately say biggest fight of all time by a mile. There's a problem with it though. Both Ali and Tyson had mainstream appeal but they were also considered the #1 fighter and biggest attraction in the world at in their respective times. They couldn't really coexist with one being known as "the greatest of all time" and the other "the baddest man on the planet". They were clearly the biggest names in the sport, but one of them would have to play the role of the up and comer. Even if politics got in the way of the fight which let it build over time, neither guy would have been able to build the same reputation they had while the other was active.
Foreman vs. five scrubs in Toronto was able to draw 30 million viewers on ABC. One can only imagine how much attention a prime Ali vs. prime Tyson would grab.
In 1940, Floyd would fight Manny twice in a fucking month and nobody would give a shit. It would be shown as highlights between war newsreels. It only does "numbers" today.
this ^^ Ali at his peak was probably the most recognizable man alive, Tyson was not that far behind. The whole freaking world watched Ali's fights.