Ali had fast hands, great footwork, and a phenomenal chin. His flaws come more from using an unorthodox style much like a Roy Jones Jr. Ali was so gifted as an athlete he didn't need to "box" perfectly his athletic ability more than made up for his flaws as a boxer.

Meanwhile you look at someone like Marciano and his skill set and athletic ability and you wonder how he got to 49-0, its all the more amazing IMO.