A look through the stats shows he fought many boxers who were in their peaks, I know stats don't tell the full story, but he fought many people who had 0/1/2 losses on their records and were on the back on winning streaks.

See here:

Mike Tyson - Boxer

I think in his prime he would have torn apart any heavyweight ever made, his speed, power and elusiveness would have been too much for any of them. Shame he went off the rails or he would have had an incredible legacy, he would have been undisputed best ever.