After playin STALKER and Metro(even abit ARMA) I must say that the, what I like to call "Dirty russian" type of atmospheres work the best. Theres just something so desperate about it. Playing in some post-apocalyptic USA setting with some USA HORAA hero feels like im still a makeup wearing supermodel in a cartboard world, nomatter how much dirt they try to throw in my face during the cutscenes too make it look desperate. The place and people just never look shit enough(with few exeptions ofcourse) to create that atmosphere of desperation.
I agree, I think the simple fact of why is how "down to earth" the games are, games such as Fallout don't have that desperate atmosphere because of the setting, in fallout, you have lasers, robots, rebuilt society, and such, it just doesn't give that same atmosphere when your walking down a rebuilt Vegas strip that's stuck in 50s cultural, while carrying some big plasma-cannon thing. Where as metro and stalker, they are very much more "realistic" (I know mutants and anomalies aren't real, but compared to Fallout and such) they have scenarios which seem like they can actually happen. Along with the fact that these games main selling point is there atmosphere.
Another reason, could just be because its Russia, you really can't think about Russia, without thinking about the Soviets and nukes, and for a long time, Russia and its surrounding countries, really where that "dirty", it was hard times back then in those places