The lights are on
I might be wrong on this, but I think that also has a lot to do with the current generation of gaming just being over-saturated with FPS games. I can especially understand why people would like FO3 if they never really played the old games first, or if for whatever reason they just didn't get into the older games.
I see your point, but for me I don't really have that kind of problem. I think on my part it also has to do with how my library of current generation of games is extremely small. I just don't have much interest in what's currently hot on the market and still find myself going back to playing older games just as easily. Although maybe it's just more so because of nostalgia.
Anything from Blizzard, Black Isle, or Bioware for me.