I think Cotto has a decent chance. Paul Williams has a good chance and Oscar maybe in a rematch depending he looks good at 147lbs against Pac. Other than that....NOBODY :deal
Williams and cotto would have the best chance, i think mayweather would beat them but it would be close
Ray Leonard, Ray Robinson and Hearns. I'd pick these guys to beat Mayweather. SRL and SRR both were simply too tough for Mayweather and could match his speed, even if Mayweather would be technically better. Hearns imo would be able to keep him at a distance and box him all night long.
PBF won't lose to anyone ... Margarito, Cotto, Mosley, DLH, Pacquiao, Hatton, Williams, all display weaknesses that PBF will expose if he ever were to fight them. I don't see anyone out right now beating PBF ... it would have to be a noticable size mismatch ... he would have to go up to supermiddleweight and fight Joe Calzaghe.
Wait till after the ODLH-Pacquiao fight. If Pacman can take Hoya's punches, then everything will be on another square board for a Mayweather-Pacman bout...
Pacquiao v Hatton would have to come first because PBF isn't going to fight till it has been 2yrs since his last fight ... and it would have to be against the P4P best fighter or the best fighter at or around his division. PBF is the madatory challenger to Vernon Forrest's belt being the champion emeritus at 154.
All-Time? Duran (definite imo) Robinson (definite imo) Pryor (definite imo) Arguello (definite at SFW, lean towards Mayweather at LW over 12, Alexis over 15) Chavez (maybe, though seeing what sorta fits fast in and out guys gave him it's not a certainty, though I'd favour him over Floyd at 130, 135 and 140, Floyd at 147) Hearns (Bad matchup for Floyd, he would either get destroyed or lose a wide UD) Mike McCallum Kid Gavilan (would just walk through Floyd's offence, seems like a light puncher in record but back in those days fights were allowed to go on longer; I reckon Gavilan would beat Floyd very badly tbh good technician aswell) There are many others, yet there are others who Floyd would beat. Not flaming him, just giving a response to the question.
Oops, nowdays I'd say Williams would be a nightmare for him at 147, and at 154 also (Williams will probably be more happy at the weight imo) Can't think of anyone who would definitely beat Mayweather, but if he rebounds well I'd say Cotto would give him a hard fight. I think Margarito would be too one dimensional to beat Floyd, though with his style you can't really count him out completely against anyone at 147. I'd expect Floyd to win a wide UD. Might look similar to Pavlik-Hopkins in terms of punches landed each way. Saying that though, margarito would be constantly throwin,g unlike Pavlik in that fight, so who knows? If Floyd came back tomorrow and fought Margo instead of Sugar Shane, I'd say it's 60-40 in Floyd's favour.
Right now? Williams, maybe Margarito, maybe Cotto. Mayweather would beat Casamayor at 130 or 135, would be old Tszyu at 140, would beat Spinks, would beat old Mosley (lightweight Mosley would be tough), etc.
I think Floyd would hit Margo at will and would win a wide UD,no doubt in my mind.He would beat the rest at 147 also(Clottey,Berto,Mosley,Cotto)Williams would be the toughest fight for him but I still see him winning a decison against him.