When comparing the respective 6 month launches of Wii, PS3, 360, PS2, Xbox, GC, PS1, N64, here is what we are learning about this generation.
Wii, PS2, and likely N64 sold over 2 million consoles in 6 months (Oct-Mar, Nov-Apr).
Adjusted for USA population growth in 2006-2007 from to 2000-2001, Wii is outselling PS2 by roughly 10%.
Following these two launches, are the 'typical' launches of successful consoles - Xbox, 360 & GC.
These 4 consoles sold in relatively sustainable numbers, although each experience dropoffs in times of competition after launch hype and the holiday sales spikes ware off.
Lastly, the 'bad' launches are Gamecube, PS3, and PS1 all of which average under 300,000 per month for 6 months, despite launch hype and holidays.