Last January, then-independent publisher Activision announced that the Guitar Hero series--which it purchased in 2006 for nearly $100 million--had generated $1 billion in sales. This month, the now-half of Activision Blizzard announced that it has sold $1 billion worth of units of a single game in the rhythm-game franchise, Guitar Hero III: Legends of Rock.

　　Although Activision Blizzard's World of Warcraft has generated more than $1 billion in revenue thanks to its 11.5-million plus monthly subscriptions, Guitar Hero III is the first to reach nine-digit figure in worldwide retail sales alone. It was helped to the milestone by the game's various configurations, which included a la carte software and pricier guitar-peripheral bundles.

　　News of the $1 billion milestone first surfaced at last week's Consumer Electronics Show, when Activision publishing president Mike Griffiths mentioned the figure. According to UK-based Edge Magazine, Griffiths also revealed that to date, 21 million songs have been download through Guitar Hero games, 9 million less than the rival Rock Band series. The executive also reportedly said that more than 141,000 songs had been composed and uploaded via Guitar Hero World Tour, the new multi-instrument installment in the series.