I’m reminded of a few years ago when a high up developer at (if I remember correctly) Epic games was giving a keynote at GDC and was trying to make the point that hardcore gamers didn’t buy the Gamecube and asked "How many of you own the Gamecube?" ... I don’t think he anticipated that a good 50% of the crowd was going to raise their hand.
While there are gamers out there who are motivated to buy a new console strictly for the advanced processing power, a large portion of the most dedicated gamers are motivated to buy an additional system because it offers a gameplay experience that is unavailable elsewhere. In previous generations Nintendo was able to appeal to this demographic because Nintendo (and their second party developers) produced games of unmatched quality in many genres which were not heavily focused upon, and this generation they have added to that with a unique user interface and an unprecedented focus on social-gaming. Personally, I wouldn’t be surprised if somewhere between 25% and 50% of people who own an HD console also own a Wii; and the Wii is getting similar use as a videogame system as their HD console gets.
You can see how a lot of the elitist gamers who have become entrenched in the videogame industry as a designer, developer or “journalist” don’t understand the values of a lot of gamers who own the Wii by how they talk about certain gaming features. My favourite example of this is how many of them talk about how local multiplayer is obsolete, and developers should only consider local multiplayer if online multiplayer is complete and polished. These people can’t seem to understand that some games are seeing unprecedented sales (Mario Kart, New Super Mario Bros. Wii, and Mario Party 8 for example) because people are buying them explicitly for their local multiplayer.