I finished Doom III two days ago. What a scary game.
I am generally easily scared by scary movies, and Doom III have that really scary feel to it, like a movie. It's beautifully made and they make really good use of the shadows and the fact that none of the weapons in the game can have a flashlight attached, it would help so much – and that's exactly the point, it shouldn't be too easy. There's nothing like entering a completely dark room and hear the characteristic sound of zombie footsteps closing in, changing to the flashlight and locate the zombie, back to the trusty old shotgun and shoot in the dark, back to the flashligt to check…
I don't think I managed more than 15 minutes at a time before I had to take a break the first 10 days. Later on I became more desensitized, so I could do over an hour of slaughtering hellspawn monsters in one stretch. That was good.
But even with all the excitement from all the well crafted scary effects and scenery in the game it did become kind of dull for the middle part, the monotony only broken by the trip to hell, but even that was getting dull before it was over. The final parts in the caverns and excavation did make it a little more exciting again, mostly because there's more challenging monsters, and because the storyline is coming to a conclusion.
In the end I feel a little let down by it, I had expected more, but I guess I'm more of a Splinter Cell man myself. For that reason I'll probably buy an Xbox 360 sometime when the price come down a little, maybe get it bundled with the next Splinter Cell game.