Microsoft’s Halo:Reach generated $350 million in revenues in its first 16 days on the market, according to Microsoft’s earnings call today.

Those worldwide sales numbers make it one of the biggest hits of the fall video game season. Other big titles include the upcoming Call of Duty Black Ops game coming from Activision Blizzard on Nov. 9. Other big titles include Star Wars the Force Unleashed 2, Fallout New Vegas, Civilization V, Fable III and Medal of Honor.

Microsoft did not say how many units of Halo:Reach it sold in the second fiscal quarter ended Sept. 30. But if each game was priced at $60, then the revenue number suggests the game sold 5.8 million units. The number is likely less than that, since Microsoft has special editions it sells for higher prices.

The company said previously that it sold more than $200 million in its first 24 hours on the market. That’s a blockbuster by any standard, though it isn’t as high as games such as Call of Duty Modern Warfare 2, which was the biggest selling game of all time. The Halo:Reach number is probably pretty close to sales of Halo 3, which sold an estimated 5.2 million units in its first two weeks and more than 8 million units by the end of the holiday season in 2007.

The upshot is that Microsoft will likely have good results during the current season. In the second fiscal quarter ended Sept. 30, the company said it sold 2.8 million Xbox 360 video game consoles, up 38 percent from a year ago. The Xbox 360 has been the No. 1 console in the U.S. since it launched a redesigned model in June. Overall sales were $1.8 billion in the quarter for the company’s Entertainment and Devices division, which includes games. That was up 27 percent from a year ago.