The thing about this movie is that it just feels like the video game. Even if the whole movie is just crazy, off-the-wall situations and violence, that makes it no different than that game, right? People who like the game will like the movie, and that never seems to be the case these days.
I don't really know.
On a side note, I personally hate Team America, but I think anyone who liked that movie would like Postal as well.