Probably far fewer than never had the opportunity to realize they could be great in the first place.
If greatness is one in a billion we have 8 (boy would the richest like us to believe that!). If it’s one in 100 million (I’m bad at math. I think it’s like) 80. Or if it’s one in a million, that’s 350 in the US alone. I’m inclined to lean toward the later, after all, if there aren’t a lot of greats waiting to be called up, how the fuck did we beat the odds by such a large margin??