Interesting essay here (h-t m'mate Craig). Discuss. (I may update with my own reflections later; just back from birthday weekend, playing catch-up.)
UPDATE (as promised/threatened): I'm very much appreciating the comments.
As Lee says, horror has a strength in depicting the ugly; it also busts open the universe, in depending for its metaphor on the premise that what we see isn't all there is. I totally agree with Libbie that the slasher-type films have little or nothing to say for them, at best.
I've long noted this, however: horror is long on depicting the dark, but virtually never even tries to depict The Other Side. That is, the devil (and his homies) are vivid, active, present, and powerful -- but they're either countered just by people, or "good" monsters (Hellboy), or ex opere operato religious icons (the more Roman Catholic tellings of Dracula, Buffy). In fact, a vampire asks Buffy about God, and she says "The jury's still out." In fact, her creator, the brilliant Joss Whedon, is a self-described "angry atheist," but he finds himself in need of religious icons to have something to fight evil. The "something" is amorphous and non-specific, and arguably often immoral itself, but it's something.
Only a few such as Constantine and Bram Stoker's (F. F. Coppola's) Dracula do much more than hint at God. It has taken Christian writers such as Frank Peretti and the vastly superior Ted Dekker to bring Him into the story.
Is it possible that there is a C. S. Lewis out there to do for horror what he did for allegorical fantasy (Narnia) and science fiction (Perelandra)?
Resources: Christian horror writer Maurice Broaddus has written about the field, including A Theology of Horror, and some additional thoughts. (I've not yet read any of his fiction; has any of my readers?)
Ted Dekker also has a web site.