Doom 3 is F'ing Scary!
The gameplay is simple and straightforward. Move, shoot, unlock doors, get PDA information (emails, video files, audio files), listen and look at the PDA files to figure out door codes, hidden goodies (BFG!), etc. The lighting is the most incredible thing I have seen videogames do. Period. A second Period is needed for emphasis. The graphics are AMAZING! I have a GeForce 4 64MB 4200 ti and am running my Athlon 64 3200+ @ 2.2GHz, and 768 RAM. Nothing really over the top pro gamer or anything like that, and I have it at medium detail settings and 1024x768 and it is TEH SHITZ0RZ!!!!
The scary parts are scary when played at night, I'm not sure about the difficulty settings yet though. I started playing hard, which was too hard until I learned the game, and by that time I started over at medium, so I can't really judge. Also, the gameplay is different than the first two (duh). There is less throwdown action, and more creepy movement and lighting and sound tricks, punctuated by brief firefights with some scary shit! Right now the game is too easy for me, but still fun, so if anyone gets it, play as veteran rather than marine! Of course, the game is still young, so I might just be eating my words here in a little bit...
All in all, I would say it is the next must have game along with Half-Life. A solid A!