I may not have taken any fancy creative writing classes in college, but the way I see it, if you want to tell a successful story, you have to have a likable character. Of course multiple likeable characters would be ideal, but I'm just asking you to take baby steps here, Hollywood. When you make a movie with a cast of about a dozen people, you should try to make at least one of them be likeable in some way that transcends "nice tits."
In The Hills Have Eyes, there are only two groups of people. The first are the horribly mutated, cannibalistic hangers-on of a mining town that was too close to a US Department of Energy nuclear test site somewhere in the New Mexico desert. The others are an extended family of bickering, suburban assholes on a road trip gone wrong. You quickly establish a unique reason to hate each and every one of them.
It is impossible to build effective conflict between two groups that the audience hates equally. An audience likes to see good people do bad things to bad people, because it serves a sense of justice. They had it coming. In a perverse sort of way, an audience likes to see bad people do bad things to good people. Harming the hero is what makes them bad, and justifies the hero's action when the tables are ultimately turned. But when bad people do bad things to bad people, all you have is bad things happening for the sake of the bad things. This movie quickly degenerates into a senseless visual white-noise of blood and gore. There was no joy to it, even on an ironic or subversive level. It felt like watching a televised execution.
The makers of The Hills Have Eyes seem to have also forgotten that a movie has to contain some scenes that are, even in some small, cursory way, enjoyable to watch. I'm not saying that everything has to be sunshine, lollipops, and rainbows. I'm just saying that there has to be a certain percentage of scenes that you come out of feeling like it was worth it. The remake of The Texas Chainsaw Massacre was a violent, gruesome film, but at least it created a mood. There were scenes of legitimate, gut-wrenching suspense in-between the obligatory running and screaming. The Hills Have Eyes has no emotional highs or lows. It's just a string of grisly murders glued together with cheap scare tactics ("Hey, let's focus on a character in the middle distance, and then HAVE-A-SHAPE-BLUR-PAST-THE-FRONT-OF-THE-C
(SPOILERS) When Freddy Krueger rips a dude's muscles out of his arms and legs and then dances him around like a marionette, that's a horrible, gruesome thing to watch. But, even as he's doing such awful things, Freddy still has a certain charm. You still leave the scene with your inner fourteen-year-old thinking, "Whoa, that was awesome!" When two savage atomic mutants are raping a pair of unlikable sisters while holding a newborn baby at gunpoint, ultimately shooting one of said sisters in the face point-blank, you suddenly don't feel like you're going to be recommending the movie to your friends.
How many times do the family's dogs have to run away, requiring a lone character to stupidly chase after them into the dark unknown? I would say, "One time, max." The writers of The Hills Have Eyes would say, "Approximately once every ten minutes for the first half of the film."
I don't think it's required to have a love interest in a horror film, but I do think that a consensus needs to be reached whether you're going to go there or not. For example, I don't mind if your movie has two sexy teens spending many moments of abject horror/momentary victory clinging to each other on the verge of passionate make-outs, but if you're going to do this, I would humbly suggest that the two sexy teens shouldn't be brother and sister.
If I were to write out a diagram of this movie's pacing, it would go something like this:
Boring, boring, boring, annoying, boring, HORRIBLE!, GHASTLY!, DEPRAVED!, boring, boring, stupid, boring, AWFUL!, GRUESOME!, preposterous, disappointing.