Want to keep your brain in shape? Learn a second language or...play video games!
Interesting research suggests that something about the way the brain processes information when playing video games confers a benefit equivalent to that gained from bilingualism. The researchers theorize that it has to do with multi-tasking and refined control over attention (both being able to juggle objects of focus in the multi-task as well as block out unwanted stimuli when needed).
This makes intuitive sense to me. Gaming requires both a high degree of coordinated cognitive attention, especially on modern controllers that have 13 different ways (or more) of inputing via the multiple joysticks, triggers, d-pads, and buttons. But there is also a lot of problem solving and social interactivity going on. When I'm playing Ghost Recon with friends on Xbox Live, we are either communicating about strategy and tactics or bullshitting about whatever it is we are joking about. I mention it just because it is an extra layer on top of the demands on my brain for evaluating the situation on screen, plotting an immediate response, and then navigating the controller space to get the response that I want.
All in all, I'm busy using my brain when I game. Perhaps that's why I have trouble watching movies, as they don't stimulate me enough.