If Mike hadn't lost Cus so early into his career, and then foolishly sacking his coach (Kevin Rooney), I believe he would have turned into the greatest boxer of all time, any generation.
There's an interview with him where he discusses him in his prime vs ali in his prime, and he thinks he has absolutely no chance of beating him, due to ali dodging long enough to take him out into the later rounds and drown him, like he did with everyone. I think he's being respectful of the GOAT though there, I think in his prime, he absolutely would have caught ali, and I know ali got hit very very hard by frazier/shavers/norton/foreman in his career, but he never got hit by anything as ferocious as what Tyson could put out. I think he'd have ko'd the GOAT early doors.
Prime Tyson is the greatest 'fighter' of all time, no one anywhere near close.
Tyson is nowhere near the greatest boxer of all time though.
**edit**
Worth noting that the greatest, Ali, lost a few fights in his prime vs other fighters in their prime. That didn't happen to Tyson apart from the buster douglas fluke, he was way out of his prime when it started going downhill.