Not to keep stirring the pot (although I am more and more seeing my role here as partly taking on unpopular positions, in order that they are at least represented;) but where do artists like André Gide, and more importantly, Sartre, fit in?
Gide's "Oedipus" and "Theseus" are legit--they certainly rise to the level of the great mythological literature of Antiquity, which was, in part, commenting on the contemporary society of the times.
Sarte's "The Flies" is easily in the very top echelon of mythological literature. (In some sense, Sartre is continuing Euripides' work of "deconstructing" Aeschylus, and Sarte may not be Shakespeare, but was a skilled dramatist in addition to being a philosopher.)
Even in antiquity, the cannon is largely comprised of artists and scholars (σχόλιον) commenting on their forebearers of centuries past.
I also think D'Aulaire belongs beside Aesop, and has become "canonical" purely by reason of influence, by which I mean D'Aulaire is likely one's first contact with Classical Mythology, and thus his work is taken to be canon.