I think gaming is just a fad that many people will grow tired of once they've been at it for a few years. Of course there are some who persist with it for decades.
I've been a console game for just three years and its starting to grow thin. (Before that it was just the nintendo gameboy for me in the 90s) Its because I've seen almost all the tricks and fancy bullet points in games now. I picked up the PS3 because of GT5 and Killzone 2. Ehh, now they're just another game to me. Of course there have been unexpected gems like Valkyria Chronicles, COD4: MW (face it, this game was awesome, the rest of them are crap though), FIFA 10 (my first FIFA in a decade, finally a decent football game), Red Dead Redemption (yippee, finally a good western, why do people hate this genre?) and many more. But after a certain point, its just the same old same old. I don't expect to continue gaming past this year, at least not on a daily basis.
On a side not, look through IGN editor's choice list for any console and you will find only a few top ranked games that interest you. The games we look forward to the most often turn out to be a disappointment (KZ3, GT5, COD MW2, NFS FF XIII etc etc) and I think this sentiment might be in part due to fatigue.