The argument often made, is that a lot of those were way past prime or at a weigh they wouldn't normally fight at. I'm not getting into that debate; I don't have the time! I'm just making the point others might
Even so, Mayweather still has a hugely impressive record. You might argue he ducked certain fighters (Margarito, Pac) or engineered every possible advantage on the scales (Canelo, Marquez), but you can't deny the quality of opposition.