Saturday's bout between WBC/WBA welterweight champion Floyd Mayweather Jr. (left) and WBO welterweight champion Manny Pacquiao was billed as "The Fight of the Century." Even though boxing has steadily lost public traction over the last decade, the Sweet Science has provided some of the most vivid memories in American sport. Depending on the generation, grading boxing's greatest matches still sparks debate: Muhammad Ali-Joe Frazier? Marvin Hagler-Tommy Hearns? Joe Louis-Max Schmeling? Here are a few great moments (and highest-paying meetings) from the squared circle: