If they fought today, Usman would probably win. I know there's a ton of hype behind Khamzat, but he'll lose a decision if he fights Usman right now. The jump in competition would be too much IMO. He needs a few more fights. I would favor him in the rematch though.
As for GSP being the GOAT welterweight, Usman would need to dominate a couple more years. He's probably too old to do that as a WW. I think he'd beat prime GSP in a hypothetical match up, but GSP has a much better resume and is still more accomplished in the sport at this point. You also have the whole nostalgia thing. I mean, look at how many people on here think Fedor is the GOAT heavyweight for basically beating Big Nog and Cro-Cop. It's laughable when you really think about it, and Fedor is probably my all time favorite fighter.
What's really going to hurt Usman's chances of being looked at like the GOAT is GSP coming back after 5 years and taking the middle weight strap. Yes, it was a favorable match up, but that was pretty legendary. If Usman beat Khamzat and then went up and wrestlefucked Adesanya before retiring, he would have a good argument. I think he would beat Khamzat if they fought today, but Adesanya would definitely tool him up on the feet if he couldn't take him down at will. while I do think Usman would take Izzy down, I don't think he could keep him there, and eventually I think Izzy would hurt him the same way Anderson did to most the great grapplers he faced. I think people are confused about Izzy's take down defense and grappling from the Jan fight after seeing a MUCH bigger man control him. Usman is a beast, but he's not walking into that cage weighing almost 230lbs. Jan is a true monster tor a LHW.
