Sometimes you have to go through a few reviews of a game that you've played to try to find something that puts your feelings into words. It took a while but this one seemed to hit it right on the head:
[...] Its scary. If you have heart conditions, do not play this game. Buy it, but don't play it. I have never been more scared in my life. When I first ran into the main baddies in Halo I was scared for a little bit, but eventually I just ripped into them. In Doom3, from start to finish I am one scary creature away from pissing my pants.That pretty much says it all. Well, almost all. Can you tell I've been playing a lot of this game lately? :)
The sound is also top notch. In stereo I still could tell there was a creepy undead marine behind me. If you have a 5.1 setup, prepare for an aural orgasm.
... not once in Doom3 was I sad that I would have to go into another room, scream like a little girl, run back out, collect myself, and then go forward.