Literature vs. Fantasy

What is common between Stephen King's Gunslinger series, Greg Maguire's brilliant novel "Wicked", Jasper Fforde, and Susanna Clark's Jonathan Strange and Mr. Norrell?

These are books that have transcended "Fantasy/Genre fiction" and gone into pure literature and great reading.

We've all seen the recent spate of novels that use werewolves, vampires and other fantasy props. I've had trouble explaining to people why I read fantasy, as sometimes they can only relate fantasy to Twilight or Harry Potter (I have nothing against HP, it is pretty awesome!). However, describing the genre to someone else, perhaps a fantasy beginner, is difficult without running into standard "werewolf/vampire/witch" mindsets.
Even for an author, it must be difficult to break out of these tropes.
I'm reading a book called The Secret History of Fantasy, edited by Peter. S. Beagle. The stories contributed are all strange, awesome shorts that go beyond the typical fantasy trope of evil warlord, brave n00b boy with friends.
It is rare to find a truly original writer these days, but this book has a solid collection in one place. I've discovered some I hadn't heard about and I'm sure you would too!

What books do you think transcend Genre? Which authors consistently surprise and awe?