How it affects real life: Makes the real world seem so... restrictive.
As any opportunistic politician will gladly tell you, kids can't help but reenact their favorite scenes from video games, especially grotesque depictions of violence. While that may be slightly alarmist, we can personally vouch for the cathartic breath of fresh air ingested each time we set off a whirlwind of chaos in Liberty City. Problem is, if you spend too many hours (as in 100-plus) beating peds, jacking cars and freely running through the virtual streets you'll find yourself claustrophobically reserved when you step out onto an actual city street.
Above: Probably a bad idea
While strolling through a real street after rounds and rounds of GTA IV, we had serious compulsions to hop on parked motorcycles and peel out in a puff of rebellious smoke. Sadly, reality stepped in and reminded us that you need "keys" and "permission" to do such a thing. You also can't rough up random strangers or cut through an intersection with no regard for traffic signals or police interference. Drag.
So, as with Tony Hawk, too much GTA alters your perception of the world around you. GTA IV does it even more than the previous games thanks to its grittier, more authentic take on city life. Everything just feels weird after playing it too much.