people (like myself), Ali was bigger than boxing. He showed the strength of his character by openly refusing to cooperate in an immoral war in Vietnam. Two of the men he had enjoyed friendships with -- Malcolm X and Rev. Martin Luther King, Jr. -- were gunned down. He scared many people (such as FBI Director Hoover), and a part of the American population hated him. Yet he took a bolder stand than even Nation of Islam leader Elijah Muhammad recommended to him.
Ali's fights were "events." His rivalry with the great heavyweight champion Smokin' Joe Frazier will always rank among the greatest in all of sports. And so my favorite Ali event would have to be when, at age 15, I sat ringside in Madison Square Garden for the Ali vs Frazier II bout.
Ali was prevented from boxing in the three and one-half years that represented his physical prime, and so different people pick from two very different periods -- the early and later sections of his career -- to identify which fight they believe Ali was at his peak in. I'd take his 5th title defense in 1966, against Cleveland "Big Cat" Williams. If you're not familiar with it, the film is on youtube.
Ali seemed electric that night. Williams was the biggest threat, other than Sonny Liston, that Ali would fight in the first half of his career. He was big, strong, and one of the sport's hardest punchers. Ali fights him slightly different than he did anyone else. On the film, you'll note he frequently jabs to the body, and mixes up his switching from moving from the left to the right much more than usual. Also, you'll notice that he ducks to the side numerous times in the first and second rounds. He lands his punches at a remarkably high rate. I don't think any heavyweight could have competed against that Ali.