Or Zombie rules...
I'm a firm believer that a good horror movie, (be it zombie, vampire, or werewolf), should make rules to govern it's world and should not stray from those rules. It's this adherence to the laws of that movie that will make or break it for me. For this reason I have to say that my favorite horror movie is "28 Days Later". Here's a short list of what I liked and why:
They are not really Zombies, they're infected and crazy. (For some reason crazy is much more scary than evil to me)
They can starve, they can bleed to death because they are still technically alive.
Because they are still alive they're not slow. They're crazy and don't feel pain so they will chase you until their body gives out.
Infection takes less than a minute and unlike every other zombie movie I've ever seen, they don't deviate from this.
Other movies that were good about setting rules and following them were: Night of the Living Dead, Dawn of the Dead, (Except for the end when the talking head was found in the cooler), Silver Bullet, From Dusk Till Dawn, The Lost Boys, and 30 Days of Night.
Major offenders of their own laws that come to mind, (though not necessarily BAD movies), were: Blade, Land of the Dead, Van Helsing, Buffy the Vampire Slayer, Bloodrayne, Bordello Of Blood, and Resident Evil.
Jerry's final thought: Can Jason be considered a zombie? He's slow. He's dead. He probably smells really bad.