I'll echo some others here-- Sandman, Eternals, Neverwhere, Fables, League of Extraordinary Gentlemen,Tom Strong, V for Vendetta, Watchmen, Persepolis, Maus, Bone, anything by Will Eisner...
and The Arrival, by Shaun Tan.
Which is downright amazing, and if you haven't discovered it yet, you need to find a copy.