You can !
It is beyond the scope of the average boxing fan, thats all.
It is only apples vs oranges when folks mix the criteria.
If you use one standard, and one standard only, it is possible alright.
It comes down to who they fought, with consideration given to when they fought..... and thats it.
To do so, you would need to be an expert on the opponents across different era's, which is difficult.
It only becomes impossible when folks mix in additional criteria.
It is more correct to say this.....
..... It is only possible to compare fighters from different era's if you remove the fluffery and solely focus on who they beat, and when.
Folks add in, P4P, lineal, and a whole bunch of ridiculous criteria that did not even apply back in the day..... they consider P4P, which is completely theoretical..... they consider lineal titles, despite many greats never fighting in an era where they had/needed a lineal champ..... they consider the amount of divisions from the 17 available, despite there only being 8 back in the day, and despite the fact that heavyweights only fight in 1 division.
The true students of the game deserve more credit.
While you make some pretty good points I still disagree that you cannot compare fighters from different eras. My main reasoning behind this comes down to the huge strides in sports and health science; I believe that athletes today, especially fighters, have a bigger advantage because of these advancements. While many fans might jump at me for saying this, I believe that boxers today are better because they take advantage of the science: better nutrition, better training, and none of the myths. With that said maybe the legends of the past would have been that much better had they too had the advantage that fighters today have.
I do agree that there is a lot of fluff, politics, money, nationality, and even skin color that come into play that shouldn't. A true boxing fan should hope the best man wins, but I think, in my most honest opinion, that skin color and nationality have a lot to do with it.
Truth is no one knows and no one will ever know who the best was/is, that is the only fact. While it’s fun to argue it’s more fun to sit back with friends, have a few cold ones, and enjoy the fight.