In the past week or two, I have seen two contemporary horror films of very differing styles and, in my opinion, quality: "Paranormal Activity" and "The Descent part 2".
"Paranormal Activity" is, of course, the "Blair Witch"-style, found-footage flick about a young couple who suspect supernatural wackiness to ensue in their house, so they set up a video camera to record what goes down while they've got their heads down. What ensues is a catalogue of tried and tested Haunted House gags which slowly escalates into something genuinely surprising and creepy.
"The Descent pt. 2" is a sequel/rehash of a movie called "The Descent", surprisingly, in which a bunch of thrill-seeking ladies went caving and got mostly eaten by what appeared to be Gollum's extended family. Pretty much the same thing happens in the sequel, except it's the rescue team that goes after the women that's getting munched on.
Both films set out to unsettle, shock and scare the viewer, both use the fear of the dark, the unseen, the unknown to create atmosphere, but it's how they pay off the apprehensive tension that separates them.
"The Descent" falls into the typical sloppy horror film trap of thinking LOUD NOISES are scary. It's the kind of film that makes you jump without even realising why you're jumping. You are startled by the soundtrack going "BBAAAAHHH!" before you've even realised a monster has popped out or summat: "SHIT, that was loud! Oh, and there's a monster."
Of course, "Paranormal Activity" also relies heavily on sound design to scare, the difference being that the scary noises are actually diegetic to the action on screen. The audience and the characters are hearing the same thing and are therefore unified in their "SOMEBODY'S COMING UP THE STAIRS!" terror.
"Paranormal Activity" is a resolutely old-fashioned horror film, slowly building to a fever pitch and unleashing its secret weapons only when the time is right. This is not going to win over many contemporary horror fans looking for the next slapstick death-scene or "BOO!" jump-scare, but it creeps quietly into the open mind and sits there, festering in the imagination for a long time after the lights go up.
"The Descent" is less old fashioned, coming across as one of those "more-but-less-of-the-same" horror film sequels from the 80s. Nonsensical twists and contrived characters and plotting derail any empathy for the victims as they careen from one bloody set-piece to the next like chunks of meat for the grinder.
Both films go for the old jump-cut-to-black final shock punchline ending, but one leaves you going "Erm... hang on, that didn't make any sense..." and the other leaves you going going "I don't think I should sleep alone tonight. Or ever again." Guess which is which?
So, what is it that makes a film scary? Perhaps more than any other genre, Horror is entirely subjective to the eyes and minds of its audience. What fills the pants of one viewer, might simply tickle another. Freud reckoned that what scared people the deepest was the uncanny: the familiar made unfamiliar. Ordinary made extra. By that rationale, only cavers should find "Descent 2" scary. But then Freud also said we all fancy our parents, so I'm not gonna take his word for much.
In conclusion, if you like creeping dread, suggestive scares and unsettling atmosphere, have a look at "Paranormal Activity", and if you like "YAH BOO!" jumps, creepy creatures and bathing in blood, then peep "The Descent". The first one. Part 2 is just a ropey retread with none of the skill of the original.