I think Malstrom (and many others) has made the mistake of assuming that the Wii could ever manage the consistently high level of sales that the DS has ...
The DS is a handheld system and by Nintendo making it a relevant product to more and more people (gamers and non-gamers alike) it gave them the opportunity to sell to multiple people within a single household in a generation. At the same time, by being a handheld system the DS had (dramatically) higher fail rates due to people dropping it down stairs, washing it in their washing machine, or some other careless act which causes people to buy multiple systems for themself in a generation.
The Wii is a home console and while making it more relevant to gamers and non gamers alike has helped Nintendo sell more hardware, the main benefit that Nintendo has seen is an ability to sell far more software per system. Now I know people are thinking that the Wii's software sales are no better than the HD console software sales, but (from what I have seen) piracy is a much bigger problem for Nintendo this generation than their competition and yet they have still been able to maintain a very high attach rate while having a very large user-base.
