So I know Watchmen is considered one of the greatest novels of all time, but I'm wondering if there are any other Graphic Novels that you would consider great literature?

Especially if there are any inside long running series, though I figure that's more of a longshot. I'm curious, though, what people here actually think on the subject. Do any of the other Alan Moore books rank highly for you(I particularly like League of Extroardinary Gentlemen)? How about some modern indie stuff, like 100 bullets or Locke and Key?