I don't know if its a graphic novel per se, but I just recently finished Ghost World by Daniel Clowes and thought it was pretty good. It's more of a slice of life comic though.

On the opposite end of that extreme, I also really like Roy Thomas and P.Craig Russell's take on Elric of Melniboné. It has some of the best layouts I've ever seen in a comic.

Both are only graphic novels insofar as they're a bunch of 20 pages issues stapled together.