I've only played the first 4 hours or so of metro 2033 (started playing it a couple of days ago for the first time ever) and here are some of my initial impressions with it in regards to its atmosphere (crossposted from the idle thumbs thread):
One of the things that game does so well (and it's an easy thing to do when you think about it but it's rarely ever done or done well) is that when you're in a crowd of people, they're not just standing there and patiently waiting for the player to come over to finally spring to life and become your own personal disney world animatronic, like in most games of its type where the developers want you to hear every single word out of everyone's mouth. The underground shanty towns of Metro 2033 truly feel alive in a way that I haven't felt has been executed that well since the half life games. People are conversing with one another and having typical banal conversations and theyre apparently doing it on their own time, too, about subjects ranging from being hit on by men that they're interested in to recurring nightmares they're having, sometimes even having sincere moments like when a father and son discuss what their future is going to be like once mom comes home, only to hear the sadness in the father's tone increase as the conversation comes to a close, one reading between the lines and knowing that this fantasy will remain just that until the boy is old enough to understand the truth.
As another good example, I was in a room with the leader of one town and the door of the room had been left open. As the guy was speaking to me about whatever thing he needed me to do in who knows where for god knows what purpose, I could hear the crowd of men and soldiers who were sitting and hanging out by a fire outside suddenly erupt in laughter. I actually got distracted by this and felt like I had just missed out on a great moment because I was stuck talking to sir mister plot advancer and I turned my character's head towards where I had heard the laughter coming from for just a second to see if I could catch even just a bit of whatever they were talking about. And it totally hit me that that's exactly what I would've done in real life, too, that the reaction i had was a genuine, non-gamey reaction which may have only been possible because the developers didn't feel the need to make this shooter a linear explodeaton megafire shooty pop pop game that is set at 1000% action almost the entirety of the game.