My father-in-law (who had never touched a console in his life) asked about the Wiimote on my coffee table. I showed him how to play Wii Tennis. When we got home from dinner that evening, he asked me if I'd like to play again. We played for tennis an hour, then bowled for 2 more hours.
But what is really remarkable is that when I tell this story to friends, many of them say that something very similar happened to them. No other console system has been able to reach outside of the traditional "console market" the way the Wii has done since its release and that is why stores can't keep them in stock.
My father-in-law looks for a Wii every time he goes into Walmart, and there are a lot more people like him in the world than the ones counting down days until the next "GTA" release. The magic of the Wii isn't that it is selling more units than the PS3, it's that the PS3 wasn't even a competitor for the market that Nintendo has found.