Yeah, I sort of have to agree - you don't really gain much from video games. It does depend on the way you play them. If you design scenarios or maps for computer games - it's an artistic medium that one can use (and arguably no worse than any other artistic medium). If you analyze the game mechanics (villager seconds, gathering rates, and figure out things such as "can I gather more resources if I have 25 villagers before feudalling or 24 before feudalling"), then it's also useful as practice in a sort of reasoning. But the analysis is usually done by the older players on the forums, where the younger players often have little else to contribute to such theoretical models of the game. Very few who play Age of Empires II do what I have mentioned above - or even go to the associated forums.
For me, I don't think I gained that much out of my video games. I do attribute Age of Empires II to my self-studied 5 in AP World History, but that was more due the motivational factor of the game's setting than to the intrinsic content of the game. I gained more out of an online forum associated with the game though - but that again, is independent of the game.
But wait for some number of years - people will find ways to creatively implement education into games (research into it is being done now, by MIT's EducationArcade). This will be REALLY helpful for teaching students where the students get to interact with an environment, rather than passively receive feedback from an instructor. Games are such interesting artificial environments. I often implement them into my thought experiments. But in the way that they're usually played right now - they provide no educational value.
http://www.marcprensky.com is an interesting website about the benefits of games, although it's a bit extremist (and though I don't agree with him, I think that some of his points are well-taken).
The other issue is that the main negative effect of gaming is the amount of time people lose to it. MMORPGs usually have very low (novel information/amount learned/amount thought about) to (gameplay time) ratios, and they seem to be unusually popular these days (heck, given that they don't require much more thought than watching TV, I'm not surprised at how popular they are). The (novel information/amount learned/amount thought about) to (gameplay time) ratios often decreases with respect to number of days played since redundancy in stimuli (from playing it over and over again) results in decreasing marginal utility.
One of the most educational games out there - Robocode. Build your own robot using Java, and discuss strategies for the best robot. You learn about Java, AI, and get to join an awesomely intelligent community all for that.