Don't get me wrong, I still enjoy playing genuinely novel games when they come out like Katamari Damacy or Braid, but that's still not more than a few hours a year. And I appreciate that gaming can have other ancillary social or parenting benefits.
But at it's root most serious games today are designed to exploit the mechanisms of addiction. I don't think this is entirely a bad thing, it may even be beneficial to a limited extent. But if you eventually want to make your own art and contribute to the world in a meaningful way then this requires becoming fully self-actualized. And this is very difficult when you start spending several hours per day deriving pleasure from the baser parts of the brain.
That being said I'm not a neuroscientist, but this is sort of the vague feeling I get after reading some of the basic literature on both addiction and extrinsic motivation.