In the biggest launch of a game so far this year, “Gears of War 3,” from Microsoft and Epic Games, has sold more than 3 million copies in its first week.

The big bow for the third installment has propelled the “Gears of War” series past the billion-dollar mark in lifetime sales. It’s also the first exclusive Xbox 360 console title to pass that milestone (other exclusive Microsoft hits, like “Halo,” bowed on the first Xbox).

The success of “Gears of War 3” is good news for the videogame biz, which is hoping the title will be the first in a series of high-profile games that marshal consumers into retailers and reverse months of back-to-back sales slumps.

Upcoming titles include Bethesda and id Software’s “Rage,” Sony and Naughty Dog’s “Uncharted 3: Drake’s Deception,” Electronic Arts’ “Battlefield 3,” Activision’s “Call of Duty: Modern Warfare 3” and Warner Bros.’ “Batman: Arkham City.”

Microsoft launched “Gears of War 3” with more than 22,000 midnight madness events, kicking them off at Times Square’s Best Buy theater with a concert by Big Sean that was hosted by Aisha Tyler and aired on Spike TV.

“Game launches like ‘Gears of War 3’ represent the type of event that happens a couple of times each year that brings out fans in masses to celebrate,” said Chris Homeister, senior VP and general manager of the home entertainment group at Best Buy.

Game is available in three versions: a standard $59.99 disc, limited edition ($79.99) and epic ($149.99).

“‘Gears of War’ was the first killer app for Xbox 360, and the series has continued to contribute directly to the overall success of the platform ever since,” said Microsoft corporate VP Phil Spencer. “‘Gears of War 3’ kicked off the biggest holiday in Xbox history with a bang last week.”

Along with the 3 million sales mark, Microsoft also claims more than 3 million unique users have logged onto Xbox Live to play “Gears of War 3” since launch.