Depends when Ali and when Tyson. 1965 Ali would never give him anything to hit. We saw how 70s Ali did with George Foreman (another incredible heavyweight btw) and his power, would be the closest comp to Tyson, although Tyson was faster, and he had a lethal jab - 80s Tyson. 90s Tyson wasn't as fast, but outside of the earbiting, he actually became a better boxer. Razor Ruddick took him to a decision the 2nd fight before he went to jail.
Ali had a tough time taking Foreman's punches, but he did take them, and tired the big man out late. Tyson wasn't nearly as big, and I'd say he was more powerful than Foreman (and ask Michael Moorer about Foreman's power).
I do wonder if this is a Jordan/Lebron thing, where everyone who watched Jordan knows Jordan was better, but the kids don't. Admittedly, I caught the very, very tail end of Ali when he could barely talk anymore. Trevor Burbick beat Ali in his last fight, and Tyson destroyed him, but that's not really much of a good comp either.