Researchers from the University of Krems, Austria, recently performed a study in which they tried to seriously teach children things via video games. They found out that this doesn't work. Playing a lot of video games, surprise, surprise, makes you good at playing video games, but at nothing else. There was no significant "skill transfer" from game to real life, even with educational games. Even children are perfectly able to completely separate virtual life from real life. Apart from learning social skills by interacting with real other people via a multiplayer game platform, games don't teach you anything. On the positive side that also means that playing GTA doesn't turn you into a car thief and murderer.
So while direct teaching through games seems to be a lost cause, researchers from the MIT are trying the indirect approach: What if your desire to play can motivate you to learn something outside the game which is useful for the game? Thus they developed a Curriculum: Teaching Computer Science through WoW Scripts in which high-school students learn computer science and programming by creating LUA scripts for World of Warcraft.
Given how people usually use such mods and addons to make games easier for themselves, I find it somewhat ironic that science thus proves that cheating at computer games is more likely to teach you something than playing them.