Yes, haunting is a good word to describe Fallout 3. I literally got chills when I was walking around and heard America the Beautiful playing in the background. Plus I think basing the game on the 50s which is supposedly the epitome of the American Dream was a brilliant idea. While it wouldn't be any less sad to see a more truly futuristic America destroyed, there is something especially poignant about seeing this innocent idea of America laid to waste. Am I even making sense? Probably not, it's hard to put into words...
It's great that you love the game, setting, etc. Welcome aboard!
At the same time, it's sort of funny that so many people idealize 1950s America as though it was the epitome of the "American Dream." This view was also true for the rush of Hollywood movies in the 1980s such as the "Back to the Future" trilogy and "Peggy Sue Got Married" as well as during the 1970s with "Happy Days" and "Lavern & Shirley" on TV. However, the reality of the 1950s was quite different, and Fallout 3 tends to capture the reality closer then the idealized view. Specifically, the 1950s saw America emerge from WW II as one of the two major world superpowers, and thus saw the birth of the Cold War, plus McCarthyism and the Red Scare, the beginning of the Space Race, and the burgeoning clash of civil rights that would explode in the 1960s (for America, that is). "Mona Lisa Smiled" DVD includes some very good interviews and documentary information about the 1950s because there was a great effort to make the film historically accurate. The creative team explains how many "middle class" and "upper class" Americans were obsessed with portraying the perfect image regardless of the reality of their lives behind closed doors. This is probably why the image has such appeal in the succeeding decades, but the reality was still far from the image.
Bioshock also paid homage to the mistaken notion that the 1950s were some kind of ideal period.
In both instances (i.e., both of these games) part of the reason they are successful is because they are able to point out the shortcomings that people of that time either willfully ignored/suppressed or simply avoided facing (thus leading to the explosive riots and other unrest during the 1960s). Both games show the idealized image of the period plus the horrid consequences of ignoring the reality, and the contrasting views make the point without resorting to lecturing.