It is well known...
Too bad its wrong
http://en.wikipedia.org/wiki/List_of_best-selling_video_games#Nintendo_GameCube
http://en.wikipedia.org/wiki/Nintendo_GameCube
The Gamecube currently holds the record of highest attach ratio (as far as I know) for a console on 9.6
Last figures I'd heard, the 360 had 8 in the US, not sure about worldwide
P.S. Attach ratios continue to rise into a consoles like, I do realise that the 360 is likely to take the record eventually, but it hasn't yet