I prefer science fiction, but I read fantasy as well. In the fantasy genre, I like stories where the author builds a unique world with a unique culture or unique magic or something like that. The typical good vs. evil stuff or the standard fantasy with dragons, elves, dwarves doesn't really deliver what i'm looking for in a fantasy novel.
My favourites so far were:
"The Chronicles of Thomas Covenant" series by Stephen R. Donaldson (It's a total of 10 novels - two trilogies followed by a more recent 4 book series that ends the story. This is the author whose work got me into fantasy. I especially enjoyed the "Last Chronicles", which is the final 4 books of the series. For a shorter and less dark story by the same author, check out "Mordant's Need" which has a very interesting magic system that uses mirrors. Very original!)
"The Book of the New Sun" by Gene Wolfe (This is a series of 4 novels, but usually published in 2 volumes: "Shadow & Claw" and "Sword & Citadel". Maybe too series for those who enjoy "light" fantasy, but Gene Wolfe is another author who blew me away with his creativity.)
"The Coldfire Trilogy" by C.S. Friedman (A very interesting take on vampires and it takes place on a planet where faith does work - what people expect / hope for does influence what will happen.)