Speaking to MCV, director of entertainment and marketing Stephen McGill described the title's commercial performance as "staggering".
"We obviously believed in the potential of Reach, and of Halo as a franchise, but to make over $200m sales on day one is a staggering result," he said.
"The reception the game has received has been phenomenal. Halo: Reach has proved itself to be the biggest entertainment launch of 2010 and the bestselling Xbox exclusive in history."
He added: "In this first week alone over 2,000 human years have already been spent globally playing the campaign and multiplayer, not to mention the Forge and Theatre mode - that's utterly incredible."
Halo: Reach arrived in stores on September 14. The game shifted 300,000 copies in the UK in one day and went on to make over $200m (£128m) worldwide.
> Click here to read our review of Halo: Reach
