Hmm I have to admit to being remarkably fussy. As a first 'go to' choice fantasy is it for me. It used to be sci-fi but I find very little sci-fi being written these days that isn't dystopian and/or just horrible. I'm bored with dystopian futures, not only because very little new is said about them, but also because they represent such a defeatist and negative view of the world. I pick them up and think, yeah great virological/nuclear/ecological disaster annihilates the world, survivors are telepathic/primitive/advanced and need a hero to restore the world - BORING!!
Not that all fantasy is all that great either. There is also a pervasive thread, like a bad stink, that runs through fantasy that is also a rather bleak outlook on life. I tend to stay away from those as well.
I like Celtic / Arthurian fantasy but it has to be really good retelling of the stories. My favourites are still Susan Cooper, Mary Stewart and Marion Zimmer Bradley. I'm going to give Bernard Cornwall's Arthurian books a try when I get around to them. Wasn't overly impressed with Stephen Lawhead.
Katherine Kerr's Deverry cycle is amongst the best Celtic series I have read. There was another, but I read it many years ago and can't remember the author or titles but it was about a Professor transported back in time to Wales and falls in with a bunch of druids and other assorted fellows. Much like Diana Gabaldon's Outlander series he traveled through standing stones.
Other favourite fantasy authors are Daniel Fox - really excellent series based on the relationship between Taiwan and China but translated into epic fantasy. Sara Douglas' fantasy about Troy was just excellent. Phillip Pullman, Robin Hobb, George R..R. Martin, Roger Zelazny, Tolkien, Eddings, C.S. Lewis, Anne McCaffrey, Julian May, L. Modesitt Jnr, Fritz Leiber, Biran Jacques, Terry Pratchett, Terry Brooks, Terry Goodkind, Stephen Donaldson, and David Gemmell just to name a few.