Unfortunately, shooters (and RTS's) also seems to just about the only thing released these days, like 13 a dozen. I don't really get it with X-Com though, because the setting of the first two games is about as bland and generic as you can get. Their selling point is the game mechanics and when you throw those away you have nothing
The name seems to be mostly known by the "wargamer" crowd, so I can't imagine that it would be because if brand recognition either.
Maybe the Xcom setting was bland and boring, but that's why 2K can make something really good out of it.
Remember that there were tons of players that never played Fallout 1/2 or Warcraft 1/2, but were nonetheless completely excided about part 3, despite almost having nothing in common the previous games. So yeah, using an old brand and making something completely new with it does work with the masses.