67m Xbox 360s have been sold since 2005

"In effect, the Xbox is Microsoft’s profitable Trojan Horse. The console’s latest version, the Xbox 360, is the top seller in the U.S. Worldwide, since the 360 debuted in November 2005, customers have snapped up 67 million units, generating $56 billion at retail. Its sales still outgrow those of all other rivals.
Once installed, Microsoft’s real game begins. The Live service has more than 40 million members in 35 countries. Microsoft makes money selling them points they can use to rent videos or download games. An estimated 17 million Live members pay about $50 a year for a Gold membership, which gets them access to Netflix, HBO Go, ESPN and multiplayer gaming."

Source:  Forbes, 25th June 2012