We all know that it only takes a genetic decision to make a man (or a woman), but what you are pondering is what makes a good man ... a decent man ... an honourable man, is it not?
Historically, he would likely have been called a gentleman, although not all gentlemen were honourable, decent, or good.
I think if a 'true' man has good intentions, lives by an honourable moral code, and treats others decently then he can proudly call himself a gentleman. :)