I haven't played HL2 yet, but I'd have to say I think Doom 3 is one of the best games I've played in a long time. It scares the shit out of me. I intentionally play at night with all of the lights off in my apartment. I have 5.1 surround and nothing is scarier than having the lights in the game shut off, everything have a redish tint to it (you'll have to see it kind of hard to explain) and hear the "Devil" laughing. I have to stop playing sometimes because it messes with me. These are the types of games the gaming industry should be making more of
~Zach