How long until people start getting bored of FPS games?

[DirtyP2002]

I LOVE FPS. Best way to compete with other gamers around the globe. As long as Halo3 sells more than 8 million times or Gears of War (I know, 3rd person, but still more or less same genre) sells 5.5 million times, or CoD4 like 10 million times for PS3 and 360 combined, people just don't get bored of it.

by the way, could we say it is like this:

America --> FPS

Japan --> RPGs

Europe --> Sports

???