While Alan Moore is my all-time favorite comicbook scribe, I think my all-time favorite series is PREACHER by Garth Ennis and Steve Dillon.
The series is one of the most emotional, gripping, funny, and sentimental comic series ever, im my humble opinion... ;)
After that, LEAGUE OF EXTRAORDINARY GENTLEMEN I & II, STRAY BULLETS, PROMETHEA, REX MUNDI, HELLBOY, 100 BULLETS, FABLES, PLANETARY, and THE GOON all spring to mind...
Oh, and
NIGHTMARE WORLD has some great art, although the writer is a self-promoting hack. :p
Best wishes,
Aaron