Take a look at Ali's resume:
He defeated a large list of fighters, most notably Liston twice, Patterson, Williams, Frazier twice, Foreman by TKO, Leon Spinks, Foster, Norton. All hard and tough fighters, and all these fights involved Ali using different strategies, and showed the determination and will to win he had.
He was more than a boxer. He was a proffesional at boxing.
Ali lost only 5 fights, which 2 of them were bouts that shouldn't have happened (Spinks, Holmes), another one was when he was about to retire (Barbick) while the one vs Norton he really got what he was looking for by getting hit while talking during the fight. I mean to me he only lost 2 fights fare and square (Norton and Frazier), and he came back and beat them both again. Tyson never did that.
Tyson lost to every fighter that meant a threat for him, plus he never had different strategy inside the ring, just go for the TKO. Tyson would have probably lost to Ali via the "Rope-a-dope" method used vs Foreman. Hey I'm not saying Tyson's bad fighter, he was domitating as hell during 86-89, but those were 3 yearts that's it. Then he started to be dominating at beating and raping women.
Ali's dominance spanned from 64 to 78, and he couldn't fight for 3 years during the time that we all agree was his prime.
Sure the Cleveland Williams fight was a beat, that's not my point. Focus your look on the footwork the man had, the bicycles, the quickness moving around the round, the precision of his punches. Quoting Ali himself "how can you hit what you cannot see?"