The Wii and DS sell because it cators to a diferent kind of market, one that is more diverse and broad which includes the likes of avid gamers, casuals, new gamers and people who rarely game. It's a complete shift in market , the PS2 captured this crowd by being a DVD player but the Wii/DS are genuinely geared towards them and they fully see it which is why the usual parameters in gaming don't fall on these two, analysts and devs will be tearing their hair out with failed predictions until they start to realize this.