It's really difficult to place boxers across eras. To be honest, I don't really go that far down my list and do not like to do it. Same day weigh ins, different size gloves, 15 rounders, etc. etc.... Just can't compare across generations like that in my opinion. I can only base my opinion on what I've seen in my life, for my generation, and for that I say Mayweather is the best I've seen. He's obviously in the top 50 greatest, but where exactly, who knows. I really don't care enough to get into those discussions. But if you must know, to me, the greatest ever is Jack Johnson. Both for his accomplishments inside the ring, and it was despite all the things he had to deal with and overcome outside of the ring. The man still hasn't been pardoned for crying out loud.......
Firstly , stop calling himself the best ever. Never a good thing. Secondly beat the best of his generation when they are at their best , eg weight class , age etc. Thirdly fight Pacquioa
There's nothing he can do at this point to ever reach the mantle as the # 1 P4P fighter ever. No fault of his own, even if he fought those opponents that some say he "ducked," and actually beat them, he still wouldn't be considered the best ever. If he fights 4 more times and gets his record up to 50-0 with wins over Pacman, the winner of Cotto-Martinez, challenges one other champ at MW and than maybe take on whoever is the biggest threat at 147 or 154 (Thurman, Lara,) for his final bout, than I think you can make a very strong case for him in the top 10 all time. But there's no way he can reach the very top when guys like Robinson, Greb and ARmstrong have fought as many times as they have.
Mayweather needs to win the MW title to have an argument for best ever imo, if he won the Lineal title from the Cotto-Martinez winner holding Lineal belts from WW/JMW/MW concurrently, holding the record for most Lineal titles (5), as well as being an unbeaten 6-weight champ. I won't argue anyone who has him inside there top 10/5
lol Beating Pac does nothing for Mayweather. Beating one of the middleweight champs may raise him a notch or two on the atg list.
Move up to 160 and fight the winner of Martinez-Cotto. Fight Lara if he beats Canelo. Fight the winner of Porter-Thurman. That would put him higher as an ATG.
The winner of Cotto/Martinez isnt even the best MW. If he beat the winner of Martinez/Golovkin, if that happens, then that would be a serious accomplishment. He'd never do that though.