Mobile games are a very different niche, as are flash games. LittleBigPlanet is defintely a counter-example (for PS3), but there aren't too many others.
Katamari, Lego anything, narrative-type games like LA Noire or Heavy Rain, strategy-shooters like Metal Gear, Flow...I could go on. I don't feel like there's a shortage of options; I am not that great at multiplayer shootouts and as I've got older I've become really sick of horror/gore gameplay, so I play very few FPS games any more.
But I think you a very valid question of if (or when) total computer game playtime will be (already is) so dominated by mobile and browser-based games that PCs and consoles are the actual niches.
If you look at all the major studios that have been wading into mobile and social, it's pretty clear the industry has been thinking about this for a long time now.
