I can't help but wonder if Ali WAS really the greatest. Don't get me wrong, he's got insane boxing skills, good size, and the best speed. However, I wonder if someone like Holyfield or Lewis who were later tot he scene would have given Ali real trouble. Even a guy like (don't laugh) Vitali Klitschko could have given Ali real troubles. Though I do believe Ali would have beaten Tyson pretty soundly.
I sort of equate Ali to a Henry Rono, running crazy times and dominating his competition, but then some EL G 3:26 guys come along later with better training/nutrition/supplements.