Dead Space was the first horror game I played. Looking back on it now, it doesn't seem so bad. But in DS1, I was often low on ammo, which added to the scares. I was always wondering "What if there's a giant swarm of necromorphs around the corner? I only have 14 ammo things for my Cutter."
Yet in DS2, I was always doing fine for ammo. The both of them are pretty gory, though.