Another example is the most recent robin hood script that told the tale from the sheriff's point of view (that is until Ridley Scott decided he'd rather turn it into the "Maximus Meridius, general of the North, travels through time to the 14th century to save England" robin hood that came out last spring). But as far as selling the script was concerned, it was all in the twist on the familiar tale.

An important point to make is that fairy tales are in the public domain. That allows studios to make a movie based on characters that are as familiar as Spider Man or Batman but without having to negotiate fees with the massive corporations who own those characters. But it's still up to the writers and studios to make those classic characters engaging and interesting to modern audiences.

Early in my career, I was hired to adapt a lesser-known comic starring Thor...not the Marvel comics character, but the Norse god who's in the public domain. Of course, regardless of how hard I worked on that script, I learned a vital lesson. No one's EVER gonna make a Thor movie that isn't based on the comic book. And I was right. Hopefully, it wasn't because my script sucked.

@Bob: That's a really important point. With fairy tales, you don't have to secure the underlying rights because they are already in the public domain.