Most old school RPG players would be in agreement that D&D takes its inspiration from Swords and Sorcery fiction and weird tales. You don;t have to look further than Appendix N to prove this. However, the writers of those stories were inspired by other stories, many by old folktales. Today, most of us are familiar with the Brothers Grimm and their collection of tales. While they may not directly inspire D&D style adventures, certain elements of their stories do creep into the game. Certainly the monsters do, and certain magic items. Other collections of folktales, such as 1001 Arabian Nights, influence fantasy RPGs, but none as much a Grimm's fairy tales.
What would you say if there were 50 more stories that the brothers missed? How about 500? It appears that scholars have recently discovered a collection of 500 new fairlytales. It looks like some are just variations on old classics we already know, but there's a lot of material here that's new to us. I can't wait to see this in print.