I prefer keyboard and mouse for a lot of games, definitely think it is the better way to play FPS games, and even MMOs. But these days, all I want to do after work is play games while reclining. I can't reach my keyboard when I do that, so I controller support to be a really big deal. It's definitely changed the genre of games I play as well, although I was never really that into grand strategy or RTS kind of stuff.
One day I will figure out a better situation to start using the keyboard again.