Its all perspective and subjective. How could anybody know how GOOD fighters from different eras are unless you pit them against each other, which is why this whole "resume" argument is garbage. How would Jacobs or Lemieux, or Canelo do against Marvin Haglers or Durans resume? There is no fact here at all, if Marvin Hagler, or Duran were from Uzbekistan they wouldnt be ranked as highly. Where fighters COME from also plays a role.
There's two ways to look at this. The first way is to acknowledge that we can't even properly rate fighters that are active today that have actually fought the same fighters, with any degree of accuracy. I mean there were some guys that seriously thought Canelo was going to destroy Golovkin The second way is to use the eye test and to compare the various technical aspects of the fighters from different eras and come up with a comparison based on that. It can be done; it's fun, it's why we like boxing. That's why in my opinion GGG could be competitive H2H with any MW in history. He's fundamentally extremely sound. But the opposite is also true. If you look at Hagler, Monzon, La Motta etc, you can't help but see the greatness shine through. Guys like that would be bad news in any era. Good post. And you have a point. To pretend that nationalism or racism doesn't exist is being foolish. I myself am biased towards the fighters local to my country if only because I grew up watching them.