Microsoft's Halo 3

Microsoft's Halo 3 is a monster. When it launched back in September, the game sold a whopping 3.3 million units in the U.S. More recently, Microsoft Corporate VP of Global Marketing Jeff Bell, revealed that Bungie's masterpiece had surpassed five million units sold worldwide.
A closer look at the data from The NPD Group through November shows that 4.1 million copies have been sold in the U.S. With 7.9 million Xbox 360s purchased in the U.S. to date, some simple math indicates that an impressive 52 percent of all Xbox 360 owners in America have picked up Halo 3.