It's all about "perception" and quality/price, if i may...
First, the console itself offers incredible value, because it brings on the table something that no other console had: motion controls and Wii Sports in itself...
Then Wii Play was a remote plus a $10 game, Mario Kart included a "free" wheel for the price of a regular game, Wii Fit was a nice package for its $89 price, Guitar Hero/Rock Band benefited from the same kind of perception, even Link's Crossbow Training could be included in these examples, and now Wii Sports Resort is like a WM+ accessory plus a very well done game for $25...
All these may be viewed as "excellent deals" by consumers, compared to any $50 to $70 game out there...
If you add games like Twilight Princess (40 hours minimum), Super Smash Bros Brawl (tens and tens of hours possible), Okami (30 hours), Metroid Prime (20 hours), Little King's Story (30 hours), Mario Kart (see Smash, same thing), Mario Galaxy (30 hours), all these are not only console exclusives, but may be seen as great value as well...
So, the global perception of most consumers will be very positive: Wii offers a great value, plus experiences no other console could offer...
The quality/price of the hardware, and the accessories, and the best Wii games, is simply the best you may find... it's not important at all if these games sell 100.000, 1 million or 10 millions copies, the quality/price will always remain the same, and will always be an important factor in many buyer's shopping decisions...