They expanded the gaming market, generated billions of dollars in revenue for the industry (at one point, they accounted for half of it), produced most of the growth from this generation, sold unprecedented levels of software, created a new segment of games, and changed up the way people interact with games, which in turn influenced other ideas along those lines like Kinect. I'm not a big Nintendo fan, but without them, the industry would have been in much worse shape this gen than it has been a long time. You don't even have to go into the quality of their games -- which, from their own developers, has been an improvement from 7-8 years ago.
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Simplicity is the ultimate sophistication.