Its so hard to say, cause the game has changed so much. Guys like Gordie Howe or Maurice Richard or Guy Lafleur wouldn't perform like they did in today's hockey. On one side its pretty impressive a guy like Alexander Ovechkin still manage to score 45/50 goals per year in this day and age. But then he never won a cup so it kinda taint his "legacy" in a way, even if Hockey is a team sport.
Then you have some domains i do not follow much but get there own "Goat" like Ussain Bolt in the running thing. I have no interest in this personally, but from what i heard he dominate just about everybody.
In combat sports, most of the greatest eventually loose one, and you can always say some had easier competition than others.
But yes its still impressive guys like Federer despite there age are still in the top players.
I would really have trouble naming one GOAT athlete of all time.
Hell even in porn, since you guy mention it, i wouldn't know who to name "King". Peter North's cumshot is legendary and has made some of the best one man COF ever, but otherwise his scenes where never that special and the way he had to have his face filmed before every cumshots is as much as legendary as the cumshot itself. So much that some peoples actually edited his videos to remove that part... lol
Jules Jordan has always been a favourite of mine too, he did good as an actor but really shine a lot as a director in his hey day.
In any case one thing for sure, i am sick and tired of Keiran Lee... The guy is EVERYWHERE and altough i will recognize he is not a bad performer and pretty good of an actor for porn standard, it just annoys me that he is in EVERYTHING. I wish brazzers would diversify there castings of male actors.