I'm not sure if Wii Sports is "that game" in Japan... It has a 60% attach rate, but with Wii restricted by supply, that doesn't result in uber-fast sales, and makes it difficult to predict if sales end at 3 million or 7 million.
I do think Wii Sports is an "epiphany" game in the West, moreso than any DS games have been... Nintendogs is the mega-game in the West, and Wii Sports seems bigger, based on the press its getting... How many games get good reviews from retirement homes on the NBC Nightly News 4 and a half months after release?
It is significant that Wii is selling faster than DS in the early going in Japan, but whether Wii can break through to that unreal level of 100K sales a week for long periods of time is another question...
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.