Accepted fact by who? The genre description on Amazon? I'm sorry, somehow I can't seem to take a game that has me turret shooting, and fighting waves of oncoming enemies with an assortment of automatic weapons, flame throwers, chainsaws, and explosives seriously as horror.
The only thing that makes Dead Space a horror game is the aesthetic, and in an interactive medium such as games, I feel there needs to be more to it than that. Aesthetic works in film because all you do in a film is watch, but in a game, you are an agent in the production, so horror has to illicit, I don't know, actual horror and terror in the player, as the one being subjected to the events depicted. The only time I ever felt this was on my Impossible run, which was also when I decided to go for the One Gun achievement. So yes, playing Dead Space 1 on the absolute hardest difficulty available, only using what was essentially a pistol, was actually a bit tense and scary at times. But not only is that quite a few hoops to jump through in order to get any legitimate scares out of a game, the game tends to funnel ammo drops to whatever weapons you're using, which means on a One Gun run, sure you're using the Plasma Cutter, but there's a boatload of ammo laying about for it. I actually thought Dead Space 2 on Zealot, using whatever weapons I wanted was significantly harder and more tense than the first game was on Impossible using only the damn Plasma Cutter.
Anyways, point I'm trying to make is this- just because a game has dark levels, loud noises, and big scary monsters, doesn't make it horror, because there's never anything actually hiding in the dark, whatever makes those loud noises hardly ever poses a threat to the player, and if any sort of danger is faced, it can be easily overcome with a quick burst from a goddamn machine gun. The one segment that seems to be an exception to this is the regenerating Hunter that chases you for a whole couple of minutes or so. And man what a scary couple of minutes that was!
Like I said, I have a rough time taking Dead Space seriously as a horror game, because, well, there's no actual sense of horror in it. Just because the back of the box says it's horror, and the Game Informer article says it's horror, doesn't really make it horror. Because it's still missing the horror part of horror. You know? It's not... horrific?