Would have been fun to see Ali tangle with Tyson when both were in their prime.
I think that might have been a much closer fight than many traditionalists like to admit. I agree that Ali was still better, but people tend to downplay the speed and skill Tyson demonstrated in his earlier career. It was only later in his career that he started loading up and trying to throw bombs while coming in straight up. When he fought Berbick, his head movement (and upper body movement)combined with his peek-a-boo style of defence made him a very difficult target to hit. Furthermore, in his early days, he used to always lead with this rare and mysterious thing called a left jab, after which he would throw combinations (not just bombs).
Comparing him directly to Frazier, I think he might have been more effective at getting on the inside than Frazier was. My only doubt is how he would have held up psychologically if Ali managed to win several rounds in a row.