The problem in Wlad's case, to no fault of his own, is he is subjected to only fighting in one weight class, so he can only fight the best fighters in the sole division he competes at. Floyd is allowed to take on fighters from 140-154 lbs, so the talent pool is MUCH larger in FLoyd's case. When you look at their resumes since 2000 (when FLoyd was still campaigning at SFW,) FLoyd has fought through 5 divisions against several HOF fighters on his resume. I don't think Wlad has even 1 HOF scalp on his.
Mayweather is the best, but I'd rank Pacquiao higher on an all-time list at the moment. Similar in a sense that Vitali was probably better than Wladimir, but Wlad will rank higher on an all-time list. The gap in resume though between Wlad/Vitali is much, much, much bigger than that of the gap between Pac/Floyd