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Well this one's by a Canadian, but it's Brian O'Malley. Take a look at Scott Pilgrim.
Neil Gaiman: Sandman, Eternals and his run on Miracleman (or Marvelman if you can't find it under Miracleman).
Alan Moore: Tom Strong, Swamp Thing, Watchmen (which you've read), V for Vendetta, From Hell, The League of Extraordinary Gentlemen, Promethea and The Killing Joke.
I can tell you that Alan Moore Is by far one of the best Comic writers of all time, alongside writers like Warren Ellis, Grant Morrison, Garth Ennis and Mark Millar.
Well I've never followed those two particular series, but from my knowledge Mark Millar fits under that category fairly well.
For general series average readers (without much comic book knowledge) tend to like, I would suggest Runaways, Fables and The Ultimates 2
Josh Wheddon's Astonishing X-men is a must one of the best series of this century
There isn't much in comparison to Watchmen and Sandman. These series were just amazing.
Most of American comics unfortunately are somewhat oriented towards action lovers these days... just like Hollywood.