Boing Boing just ran a series called Great Graphic Novels where various writer friends of Mark Frauenfelder pick just that. It’s a quirky list, with, for instance, Jim Woodring picking Steve Lafler’s Ménage à Bughouse:
And so I'm going to recommend a graphic novel that is great because it is good, solid and delivers in spades what I most enjoy in a comic book; a comfortable mastery of the form, fun, surprises, a story I can get into and a light touch. In short its the kind of book you can flop down on the couch with of an afternoon, lie back and enjoy.
which is about as good a recommendation as you can get.