The relation between fairies and fairy tales is fraught. Many fairy tales don't feature fairies. Many tales about fairies more aptly conform to folklore, myth, urban legend or just simply superstition, not fairy tales.
Likewise, there are two distinct, well known arcs to fairy lore. There is the older lore of terrifying, cunning, duplicitous fairies. There is, too, a sentimental lore that gives us romantic, sweet fairies. The latter largely arises from a Victorian/Edwardian sensibility. The two arcs are increasingly intermingled in contemporary tales about fairies.
I tend to distinguish between tales about fairies and fairy tales. The term, fairy tale, was coined by Marie-Catherine D'Aulnoy, who did write tales with fairies. These were largely female fairies, regal, powerful, often quick to offend, but also quick to provide aid if they so chose. They wielded greater influence than kings, significant in an era dominated by the Sun King, Louis XIV. I know D'Aulnoy was winking broadly at her audience. Since D'Aulnoy gave us fairy tale, it's worth noting that the most popular tales often do feature fairies.
What about tales with fairies, though? These are the tales that draw more explicitly on lore. I not-so-secretly really enjoy Supernatural and the other night, I was over the moon to see their take on fairy lore in "Clap Your Hands If You Believe..." I think it's become my favourite episode, if only for the scene with the microwave and Dean shouting: "Fight the fairies! You fight those fairies! Fight the fairies!" I sat afterwards, pondering as you do if you're an academic, whether it was urban legend with fairies or fairy tale. Tricky. While the brothers' story seems more urban legend with fairies, particularly since they research fairies and use lore to defeat the bad leprechaun, the core tale about the 'cobbler' rings true as fairy tale.
It's cases like these that make you aware of how bendable genre is. Academics work to define. Storytellers don't worry about definitions - in fact, they're often actively trying to subvert, bend or break definition. In creating fairy tale, D'Aulnoy herself was subverting those tales that she'd inherited. Her version of Cinderella, 'Finette Cendron,' for instance, plays a little joke on the shoe-play in Basile's 'The Cat Cinderella.'
I've none the less come to see fairy tale as a literary genre (in which I do include comics, plays, librettos, film and television scripts). I'm not going to be too strict about this, though.