letsdance on 05 March 2010
http://www.joystiq.com/2010/02/10/high-speed-banking-forza-3-sells-two-million-copies/
As of Feb. ~2 million
http://www.polyphony.co.jp/english/list.html
As of December ~1.8 million.
Forza can barely outsell a highly criticized game on a system that cant seem to push SW.