I would respectfully disagree as to the level of support for Watchmen.
While definitely one of the best, I suspect that an equal number of fans would cite "Dark Knight Returns." Others "Batman Year One."
And don't forget non-superhero work. You have a lot of people who would point to the work of Will Eisner, or Art Spiegelman's "Maus."
And, if we move outside the U.S., you have the manga fans, who might cite, for example, "Lone Wolf and Cub."
