IMHO there's simply too many great fighters to put one at the top and merging an era's is impossible to me . I could go by eras, but what's the criteria every decade or whoever the best of his era was is what it depends on ???
Langford beat champions at LW then dominated the black HW scene and had Jack Dempsey ducking him. Never been done before or since.
The age pac fought at 112 was around the same age fmj flight at 112/115 in the amateur ranks. Pac and fmj always fought at the same weights at the same age. Pac and fmj ARE THE SAME Size. Fmj has truly LESS THAN A SINGLE " height on pac while pac outweigh him. The only real difference is the reach which is a game changer but doesn't make fmj hearns (reach + height) compared to pac
I think when Mayweather was born he was 7 pounds and so was Manny. Also believe Wlad was 7 pounds as well. Also when Manny was full grown 25 he was at 126 pounds. And Floyd was at 135.