But think of how much bad things they could also have done in that time...
Who says they wouldn't have been out robbing grannies instead?
(yeah yeah I've wasted probably at least a few weeks or months of my life playing games, even ones where you shoot a lot of people, and even more playing games like soccer, basketball and hockey)
One good thing I have gotten from playing FPS games is faster visual processing. It really does improve that, especially noticing more moving objects in your visual field, faster than non-gamers do. It does help when riding a bike in city traffic, and can be potentially life saving in these conditions.
For example:
http://psycnet.apa.org/index.cfm?fa=buy ... -11858-005By Spence, Ian; Feng, Jing
Review of General Psychology, Vol 14(2), Jun 2010, 92-104.
Abstract
Video game enthusiasts spend many hours at play, and this intense activity has the potential to alter both brain and behavior. We review studies that investigate the ability of video games to modify processes in spatial cognition. We outline the initial stages of research into the underlying mechanisms of learning, and we also consider possible applications of this new knowledge. Several experiments have shown that playing action games induces changes in a number of sensory, perceptual, and attentional abilities that are important for many tasks in spatial cognition. These basic capacities include contrast sensitivity, spatial resolution, the attentional visual field, enumeration, multiple object tracking, and visuomotor coordination and speed. In addition to altering performance on basic tasks, playing action video games has a beneficial effect on more complex spatial tasks such as mental rotation, thus demonstrating that learning generalizes far beyond the training activities in the game. Far transfer of this sort is generally elusive in learning, and we discuss some early attempts to elucidate the brain functions that are responsible. Finally, we suggest that studying video games may contribute not only to an improved understanding of the mechanisms of learning but may also offer new approaches to teaching spatial skills. (PsycINFO Database Record (c) 2010 APA, all rights reserved)