German researchers have found out, that video-gaming can be beneficial for some brain-functions. The probands played Super Mario 64 and a growth in regions responsible for spatial orientation, memory formation and strategic planning were detected.

http://www.mpg.de/7588840/

Probably other games have effects too, as Super Mario 64 was tested it can only be said for sure for this games. Other games may have depending on gameplay effects on other regions of the brain.

I bet that the best thing to do is to play a wide variety of genres

Usually doing different stuff instead of doing always the same is beneficial to the brain. So this theory is probably true.

Not surprising. You can learn a lot from videogames. Endless Ocean got me quite a few steps in front of the others when it comes to knowledge of the ocean. Many games have the classic problem solving too, I'm pretty sure that helps for certain things as well. Not to mention I think your imagination is better if you play games. There's probably a lot more too.