This may seem like a silly question, but just hear me out.
Which of the Fallout games has been the most recognized? This is NOT a question of "which one is yourfavorite?" ... this is a question of which one is the most easily recognizable by culture in general. Which one has the most essence to it that would allow it to be recognized even by those who haven't played the games?
For example, things like the title or box/in-game art design. Things that define the game that made it the most recognized and culturally relevant of the series, even if it is not necessarily the best one of the series.
In my opinion, it is New Vegas. Go ahead and bash me for saying that, whatever. From my observations, it seems as if the title (Fallout: New Vegas) is the most easily identified with the series, because of the combination of both the series name and the aforementioned city name. It just sticks. And when I was younger, before I had even played a Fallout game (but had seen box art for some), the box art for New Vegas was always what I identified with the most. Other things such as Benny (the man in the black and white checkered suite), and Mr. House, and the casinos and whatnot. To me, Fallout: New Vegas is just the most easily identified Fallout game by general culture. Additionally (IF I am not mistaken), it sold the most of all the Fallout games as well, which would indeed make it well recognized.
What about you, SW?