Nope - no semantics about best or greatest. I completely reject your assertion that the best athlete has to, by definition, play one of the "money" sports - football, baseball, basketball or hockey. There is no logical imperative that makes that so. I have made a case to define athleticism and athletic greatness both in terms of results in formal competition over time and in terms of what is required of the mind and body to do the sport. Then compared that to other athletes and other sports to compare the types of challenge on one's mind and body, then comparing the best in those sports to Mr. Slater. Tom Brady is in the same category. I can still argue that football is more "practicable" in a controlled environment than surfing is (or was before legit wave pools). And a football field has the same dimensions in every stadium.
It's OK though, I don't expect many to agree with me.