Nobody will remember how well Bolt ran at some lesser championships throughout the year, they will remember his world records. McGregor will be remembered as one of the few fighters ever in the sport to break the mould, that knocked out two champions in two weight classes with ease. I think he will be quite happy with his legacy. The test of greatness in a fight sport is not always black and white. He had the most fans, the biggest ppvs, the biggest media presence, the biggest influence with the UFC management, two belts and a handful of dominant wins against high skilled and high profile fighters and will retire stinking rich and with physical and mental good health. Can't really argue that that is not great.