Kingdom Come is pretty much the best superhero comic I've read. The art is absolutely spectacular, Alex Ross at his best, and the story of a near-future DCU on the brink of superhuman war is likewise excellent. It's a Superman story in all but name, and a damned good one.
Hellblazer is definitely worth a look if you want something a bit darker. It's Vertigo's longest running book, and John Constantine is one of the more interesting comic book antiheroes. Probably best to start with the beginning here, but Pandemonium, the 25th anniversary book, is my favourite.
And I haven't started it yet because I'm in the middle of exams, but I'll be reading Infinite Kung Fu soon, and I wouldn't be at all surprised if that ends up on my favourites list. I can tell you now that the art is gorgeous, and does a great job of capturing the fluidity of martial arts.