Historical accomplishments, more than anything else, qualify someone as an ATG. Sugar Ray Robinson beating numerous HOF fighters, being the greatest welter ever, and winning lineal MW titles multiple times. Henry Armstrong holding 3 of 8 available world championships at the same time and beating HOF fighters while doing it. Ray Leonard winning super fight after super fight and overcoming the odds to beat Hagler (although I feel ray lost that one). Joe Louis defending his title 23 times and cleaning out the division. Ali being the first to win the HW championship 3 times, overcome the odds to beat foreman, engage in the fight of the century and thrills in Manila, and beat the best heavyweights over 3 generations of the Holden era of heavies.