The Jodoverse - not for the squeamish, prudish or faint-of-heart:
Incal Trilogy - If you don't tolerate metaphysical weirdness or spirituality in your stories, this ain't for you. If you accept it as a given, it's well worth a look.
Technopriests - An itriguing take on what has often been an adversary.
Megalex - For me the weakest part of the set.
Metabarons - Absolutely superb. The prequel, Castaka and Weapons Of can't possibly equal this but are worth looking at. The new series The Metabaron feels like a true sequel to the first 8-book series.
Other Jodorowsky stories:
Bouncer - A set of three brutal western tales based around a one-armed gunslinger.
Son of the Gun - How far do you have to fall before redemption starts to look needed?
The White Lama - A tale of Tibetan mysticism.
Legend of the Scarlet Blades / Izuna - Supernatiral samurai tales with superb art.
The Z Word - Zombie satire, you'll wonder why no one already did this after reading it.
El Nino - A woman searches for her brother, who may have become an infamous pirate.
Cape Horn - A turn of the century story set in South America of imperialism and change, as the western notion of exploration dies.
Mandalay - A tale of two brothers set against colonial politics and supernatural forces. Guice does the art for some of it.
Olympus - A well-spun tale by Geoff Johns and Butch Guice.
Lou Cale - A set of 5 1940s detective / journalism stories with a very distinct art style.
I Am Legion - A WW2 vampire tale with Cassaday art.
Millenium - Medieval murder mystery and crime stories set at the turn of the Millennium - 999AD.
Carthago - What happens when a new aquatic apex predator is found?
Miss Better Living Through Crime - 1920s crime series combined with inter-racial politics.