Yes I'd say it was. It was more 'real' than fantasy. It was about survival and a lack of water. Sure it had the charm of the odd comical super mutant or strange character, but the world itself seemed sad, and exploding people ruined it.
Fallout is satirical. It is on the very beginning when you do your G.O.A.T exam (look at the name) to decide what you should be for the rest of your life (and you had always to choose The Overseer, clearly indicating the brainwashing at the Vault 101). The game held that tone over and over, with a chinese invasion, exploding a nuclear bomb because a city "spoils the view", a computer president commanded by a group and Nathan:
PC: You are right, my country deserves my unthinking and unquestioning support.
Nathan: Now there is a proud patriot. After all, if they could make us wrong, we wouldn't have elected them in the first place, right?
Nathan: Yessir, trust in the judgement of other people to know what is best for me. It is the American way.
OR
PC: I couldn't possibly care less about gorvernments and presidents.
Nathan: Well, we can't all care. Besides, why should we have to? That is what the government is here for, to take care of that stuff.
I think exploding heads fits perfectly with what they aimed to make.