Current tallies including only DC votes:

7 - Watchmen (fubar, forgerelli, David, silveragemm, madhatter, Yossarian, Dave W.)
3 - Batman: The Dark Knight Returns (L&C, zatara, MrTinkertrain)
2 - All Star Superman (jhalbright, Mon L)
2 - V For Vendetta (deejay, 39steps)

Honorable mentions:

Batman: The Killing Joke (Mayor Hundred)
Batman: Mad Love (Melkor)
Batman: Odyssey (wpbooks)
Batman: Year One (Benfica04)
Justice (Todd)
The New Frontier (Commish Gordon)
The Nobody (Batman)
OMAC by Kirby (John P.)
Sandman by Gaiman (quincyjb)
Swamp Thing by Moore (crom)

Alan Moore garners 11 out of 24 votes.