I don't know how people rank their ATG. I'm not old enough to have seen and judge fighters from the past. But you can't deny the man's greatness. We have to go by what they accomplished in their careers. Floyd has beaten more champions than anyone in history (it is easier to become champions these days though), 23. Soon 24 with freaking Berto lol. How many hall of famers have they beaten? Most say Floyd has beaten around 12. Personally I don't think guys like: Corrales, Castillo, Hatton, Gatti have done enough to get in, but when someone like Gatti gets in, how difficult is it really? Doesn't seem too difficult. 2x Fighter of the year by both BWAA and the Ring. Lineal Champion at 130, 147, 154 (not sure if he was lineal at 135 or 140 but he didn't have many fights at those weight classes so I'm assuming he didn't become lineal?) So when judging ATG, I think we have to look at their career accomplishments. You have to see who accomplished more than Floyd. Well imo.
Of the HOF's, Floyd has beaten De La Hoya, Mosley and Pacquiao. That's three hall of famers. All of them were legitimately past prime, considerably more so than Mayweather. The borderline hall of famers are Castillo (whereby IMO he lost in the first fight) Cotto, and maybe Genaro. The very good, but not HOF level fighters includes the likes of Hatton, Corrales as you mentioned. 2x Fighter of the year means far less in a weak era. His reign from post-Castillo to very recently, has been weak.
I'm just going by what other people have said regarding Hall of Famers. I personally don't feel like Castillo (who imo did beat Floyd in the first fight), Corrales, Hatton, Gatti, even Genaro (who did he beat?) deserve to be in the Hall of fame. But like I said if Gatti got in, how difficult is it to get in? I don't think people will remember that those guys where past their primes. Only people that grew up in this era will. I'm a younger guy so I didn't grow up watching fighters from the past, shoot I'm not even old enough to remember Floyd's early career. I can only go back and watch fights. But still who has accomplished more than Floyd? Another thing is how many ATG's have the fighters beaten. I'm just giving a criteria on how people should judge ATG's. I mean even if people don't like Floyd, I seriously doubt there is 40 fighters in all time that are better than him, right? If so I would love to see someone's list. I'm not saying is TBE either.