I don't disagree with your basic premise but I would disagree with some of your candidates. Joe Louis is one of the greatest heavyweights ever but on a pound-for-pound basis, he's not near the top. IMO, Roy Jones is over-rated and over-hyped. Really good but I think there are better. It's way too early to put GGG in that group. Duran, I agree. In following boxing for over 50 years, Roberto Duran in the mid-70s was the best I ever saw, PFP. If Duran had been 215 pounds with that skill set, he'd easily beat Ali.
Sugar Ray Robinson has to be on an all-time list of the greatest PFP fighters. He'd be at the top of mine.
Ali was a great fighter and champion but on a PFP basis, there were better fighters.
You'll enjoy these two items:
https://www.youtube.com/watch?v=kaUrm26VQh8
Duran's hardest lightweight fight:
https://www.youtube.com/watch?v=9ksuNR7pxcU
Hector Thompson may have had the heaviest hands of all times in the lighter weight divisions. His last two opponents prior to this fight had died in the ring. He did not have Duran's defensive skills.