The current tie-ratios by console through September 2009
(Note: This is only for NA. Source: NPD)
Xbox 360 8.8 Units per system
PS3 6.8 Units per system
Wii 6.5 Units per system
If you are going to compare software sales by system, you shouldn't cherry pick individual titles but should use overall sales. Also note the 360 has been on the market for a year longer than the PS3/Wii.
http://www.gamasutra.com/view/news/25740/Analysis_Wii_Software_Sales_Slow_Down_In_2009.php
Thanks for the input, Jeff.