Stupid thread. Pac didn't step up and beat scrub champions in those weight classes. It matters who you beat, so stepping up and beating the man in multiple weight classes is clearly better than chasing belts against weaker champions to Unify. Floyd and Pac where both great and both once in a lifetime talents.
The most impressive thing for me is that aside from Bradley and JMM, Pac has been giving up significant size advantages and still dominating for over a decade. That's why he's Fighter of the Year and Fighter of the Decade for me.
A complete unification of all belts in a division is a rare case and very difficult thing to do nowadays, let alone four divisions, that would be impossible. There are various factors mainly related to boxing politics that put big obstacle for this thing to happen. Even big names such as Floyd Mayweather Jr. himself never achieved it. I thought Canelo was going to unify the belt when he got all from GGG, but yet it didn't happen. Too many factors, too many rules, too many interests involved. This phenomenon makes me believe that Ring belt is more rational indication of someone being the best in his division.