According to NPD figures, Call of Duty 4 has sold over 9 million copies since its release.
Within the first 9 days of the new DLC map pack for CoD4, it was purchased over 1 million times while not only breaking DLC records but breaking Xbox Marketplace at the same time.
Also, quote from 402, “Some cool numbers we pulled recently to see just how much gameplay that actually is, shows that Xbox LIVE members played more than 30 million sessions and logged over 30 million hours of gameplay!! We’re talking 1.9 billion minutes logged in the first 9 days!!“
Source: IAMfourzerotwo.com