Excellent point, there's only so many actual stories to tell, or so the story goes...but I'm not sure we're talking about the same thing.
It's the same way with musical theater as I recently found out while writing songs for a BMI workshop (which I didn't get into) - almost all musical theater is based on an existing story.
But there is a difference between a retelling of one of the stories humanity has always gathered 'round to hear, and a remake of one of those retellings.
Again, most of Shakespeare's plays were
remakes -- not just original tellings of classic themes and structures, but actual retellings of existing stories with (roughly) the same titles, plots, and characters, or fictionalizations (often grossly so) of real historical events. Not to mention all the Greek playwrights whose plays were retellings of existing myths. Sophocles didn't invent the characters of Oedipus, Jocasta, Antigone, and so on; he retold the existing myths about them in a new form. So it's a spurious distinction. Remakes, retellings, they're all part of the same continuum, the same human creative instinct to keep old stories alive.