Call of Duty: Black Ops has crossed the $1 billion mark in sales worldwide, according to internal Activision Publishing estimates. To date, more than 600 million hours have been logged playing Call of Duty: Black Ops since the game launched on November 9, 2010. The average Xbox Live player logs on more than once a day and plays for more than one hour each time, according to Microsoft. Over half of that time is spent playing online with and against friends.

Call of Duty: Modern Warfare 2, the predecessor to Black Ops, also accumulated over $1 billion in global retail sales but it took the game slightly longer to do so. Last month, Black Ops set a new record for the video game industry by selling 5.6 million copies (more than $360 million) on its first day and then broke theatrical box office, book, and video game sales records for five-day worldwide sell through in dollars (more than $650 million).

Black Ops is the seventh installment of the popular Call of Duty military-themed shooter franchise. Activision Blizzard originally said that it did not expect Black Ops to outperform Modern Warfare 2 even though two months ago it said preorders for the former were selling faster than those for the latter did.

"In all of entertainment, only Call of Duty and "Avatar" have ever achieved the billion dollar revenue milestone this quickly," Bobby Kotick, CEO of Activision Blizzard, said in a statement. "This is a tribute to the global appeal of the Call of Duty franchise, the exceptional talent at Treyarch and the hundreds of extraordinary people across our many Call of Duty studios including Infinity Ward and Sledgehammer that work tirelessly on the franchise. Our ability to provide the most compelling, immersive entertainment experience, and enhance it with regular, recurring content that delivers hundreds of hours of audience value, has allowed Call of Duty to continue to set sales and usage records."