Where we disagree, I think, is in the notion of potential. Capacity is something that - to a large degree - is inborn. Not everyone might well reach their potential (cf. many athletes), or they might be missing some key quality to being successful, but just in virtue of having some (or all) of the qualities necessary for that kind of superlative success they are "special" in the literal meaning of the word: better, greater, or otherwise different from what is usual.
I maintain that ambition is a conscious choice. You choose to be ambitious, or you choose not to be. That ambition, combined with otherwise unexceptional characteristics, produces failure, more often than not. But not always.
Those exceptions are the heroes. The only thing that's special about them in their success, but that success is based on unexplained variance.
Ideally, we'd get to play the characters starting before that selection occurs, so abject failure is actually an option. This is how good tabletop rulesets work.