Some notable absences from the list are the apocalyptic The Sky is Falling, which will never see the light of day due to its controversial premise:
Two clerics on an archaeological dig discover proof that God does not exist; with their faith irrevocably shattered, they go on an extremely violent crime spree, which includes murders, rapes, robbing and indulging in all sorts of drugs. The Catholic Church, faced with losing their power and influence, hire an assassin to stop the two clerics before the public learns of the truth.Now that is some fucked up shit (pardon my language). Also missing from the list is Aliens vs. Predator. It sounds like a piece of crap, but AvP actually has a thoughtful premise and Dark Horse's original comic was well executed and not at all cheesy. The script is not quite as good as its source material, but its decent. Unfortunately, the project seems to be stuck in Limbo. Speaking of the Alien franchise, David Twohy's unused script for Alien3 is also worth looking at.
So there you have it. Just for good measure I'll throw you a link to Drew's Script-O-Rama, the definitive web resource for movie scripts. And look here, Samael's started a nice discussion in the Kaedrin forum about "important" films.