The following quote is taken from Halo 3 : Biggest Day in U.S. Entertainment History.
Microsoft today announced that Halo® 3 has officially become the biggest entertainment launch in history, garnering an estimated $170 million in sales in the United States alone in the first 24 hours. The Xbox 360™ title beat previous records set by blockbuster theatrical releases like Spider-Man 3 and novels such as Harry Potter and the Deathly Hallows.
Impressive for a video game. I picked up my copy at the company store on opening day at 9am. Halo 3 is a decent game for some mindless shoot-em-up fun, and the campaign is decent, though nothing spectacular. Overall, I think it's a worthwhile purchase for anyone who wants varied online gaming of the FPS sort.