Actually for most of the year Wii was very hard to find and would sell out within hours if not minutes of being placed on the shelf. Also you're making the mistake that production can be expanded that easily, either thaey have to open up a new factory, or they have to negotiate with another company to begin production, both of these tae time, it is not as simple as flipping a switch, and you are lost if you think they aren't actively researching those and other possibilities to expand their production.
NA sales put the Wii as highest and the 360 as second highest, although much further behind than the Wii, PS2 is behind the 360, so sorry it is not the second highest selling console.
http://vgchartz.com/ayearly.php
Also just because it will sell a million doesn't man it will continue to sell at this rate for the next few years, this year its sold 3 million so far in NA. over the next few years expect that number to drop, face it, it will be surpassed by the Wii by the end of 2010.
Predictions:Sales of Wii Fit will surpass the combined sales of the Grand Theft Auto franchiseLifetime sales of Wii will surpass the combined sales of the entire Playstation family of consoles by 12/31/2015 Wii hardware sales will surpass the total hardware sales of the PS2 by 12/31/2010 Wii will have 50% marketshare or more by the end of 2008 (I was wrong!! It was a little over 48% only)Wii will surpass 45 Million in lifetime sales by the end of 2008 (I was wrong!! Nintendo Financials showed it fell slightly short of 45 million shipped by end of 2008)Wii will surpass 80 Million in lifetime sales by the end of 2009 (I was wrong!! Wii didn't even get to 70 Million)