Monsters

It's my impression that the most popular monsters in supernatural horror films are werewolves, vampires, and zombies. There are countless trashy horror films, but I have in mind the more "upscale" examples. Excluding comedies, the more upscale representatives include:

Vampires

30 Days of Night (2007)

Bram Stoker's Dracula (1992)

Count Dracula (BBC, 1977)

Let Me In (2010)

Near Dark (1987)

Nosferatu (1922) 

Nosferatu the Vampyre (1979)

The Hunger (1983)

Werewolves

Dog Soldiers (2002)

Skinwalkers (2007)

The Howling (1981)

Wolfen (1981)

Zombies

28 Days Later (2002)

28 Weeks Later (2007)

I Am Legend (2007)

The Walking Dead (2010-)

1. These monsters share certain things in common:

i) Vampires, werewolves, and zombies were originally human. 

ii) Vampires, werewolves, and zombies are cannibalistic, feeding on humans.  

iii) Vampires, werewolves, and zombies are contagious. They propagate by biting the victim. In the case of werewolves, a scratch will suffice. 

iv) Vampires and werewolves are creatures of the night. If you can fend them off until sunrise, werewolves revert to human form while vampires retreat into windowless buildings to avoid cumbustion. I Am Legend combines the zombie mythos with the vampire mythos regarding the aversion to sunlight. 

v) Vampires and zombies are cadaverous. Functional corpses. The Undead. The Nosferatu variant gives vampires a more famished, cadaverous appearance (e.g. Daybreakers [2010]; Nosferatu [1922] Nosferatu the Vampyre [1979]).

vi) Both vampires and werewolves have a special kinship with wolves.  

vii) Both vampires and werewolves are shapeshifters. 

2. Insofar as the vampire, werewolf, and zombie genres originated independently of each others, it's an interesting question why they have so many things in common. Is this due to subsequent cross-pollination? Or do they reflect a common point of origin in a subliminal Ur-mythos? Is the human imagination wired to generate variations on this theme?

3. These three genres are revealing from a theological and sociological standpoint. In the past, death was all around us. Natural mortality was high, amplified by famine, warfare, siege warfare, epidemics, and pandemics. Heaps of human corpses in public view. Famine and siege warfare also resulted in cannibalism. Although less dramatic, open-casket funerals used to be the norm. But nowadays, due to cremation, modern medicine, and peacetime conditions in many parts of the world, the ugly face of death is easier to hide. And that, in turn, makes it easier for the natural fear of death to recede from consciousness.  

By the same token, travel by car, electrical lighting, and the elimination of wild predators has made the fear darkness recede from consciousness, although it remains close to the surface. Consider a child's instinctive fear of dark. Or walking in back alleys at night. Or your car breaking down on a deserted country road at night. 

So why do we create movies and frequent movies that evoke these primal fears? Perhaps because what's consciously suppressible remains subconsciously irrepressible. Even though modernity makes it easier to push these primal fears to the back of our minds, they remain firmly embedded in the human imagination. The world of nightmares. 

We enjoy scaring ourselves in a safe, controlled environment. And perhaps we feel that spooking ourselves in fantasy exorcises or inoculates us from genuine terrors. 

These genres reflect a throwback to the haunted imagination of the middle ages. They have a number of literal or analogical parallels in the medieval experience, viz. fear of death, fear of the dark, contagion, cannibalism, witchcraft. It's interesting that Nosferatu the Vampyre (1979) combines the vampire mythos with plague rats.