GT3 and GT4 actually did a lot for my car knowledge. Communikeys taught me how to type. Call of Duty 2 has a decent amount of WWII battle history. I didn't know how to beat up a prostitute until Grand Theft Auto...
I think that Tetris pays some dividends in terms of spacial awareness. Diablo II online teaches you a little bit about how to trade goods and negotiate with other people (ie: everyone is out to screw you). That one is also instructive about free market principles and macroeconomics - the spontaneous creation of currency - and the fluctuation of currency valuation due to counterfeiting and what amounts to printing (or mining if you're on a gold standard) currency.
Most realtime strategy games have a lesson in them about investment as well. But it's easy to take that lesson the wrong way. In these games, it's never wise to have any money in the bank. You should spend it as soon as you get it and constantly be at zero credits. Of course, in real life this is nonsense. But the lesson about investing in something that pays real dividends can still be valid. Money sitting in the bank can almost always be put to better use by investing in production and will give you a real return when your zerglings take over the nearby protoss base and give you access to all their energy crystals and vespene gas.
...I don't even want to begin talking about the vast quantity of computer networking that I've learned in order to make starcraft lan parties work.
Some of the early nintendo games inspired me to learn java programming and write my own game - something that actually improves my productivity at work and has actually earned me a bonus. So retroactively, all of my nintendo games were free.
That being said, what could I have been doing with my time if I hadn't been playing games? I certainly could have been learning other things. In addition, I've lost hours to games that taught me absolutely nothing. But despite that, I think it's great that anything at all can be gleaned from gaming - because in the end it's supposed to be entertainment.