http://www.pcworld.com/article/153419/software_attach_rates_for_xbox_360_ps3_wii_calculated.html
Any surprises? Just one. The PS3 had a third-party attach rate of less than two back in late 2006, just after it debuted, but Gamasutra's chart now has it nipping at the Xbox 360's heels with more than double that figure.