Question: Why doesn't story-rich game foo sell that well?
It's time management. Most people have X hours of "play time" per week and they want to maximize it. Having to surf through a 30 hour "story" that isn't really THAT great to begin with (especially when you are 25+ and have played all this crap before under a different guise anyhow) gets old.
FPS games and the like are easy to sit down and get immediate satisfaction from. Complex RPGs are not. It's not hard to understand.