Halo 3 will sell more than 4 million units in the US by the end of October, according to GamerMetrics analyst Nick Williams.
"More importantly for Microsoft, Halo 3 will drive significant incremental Xbox 360 hardware sales during the upcoming holiday season, taking the focus away from the Wii and PlayStation 3," says Williams.
With the popularity of Halo 3's multiplayer feature, Williams believes that the impact of the game's launch will be felt by the rest of the game industry well beyond the launch period. "Gamers will have little free time to play other titles during the early holiday months, meaning less attention given to competing Xbox 360 software releases," he said.
Williams also believes that Halo 3 will eventually break into the top ten best-selling videogames of all time. Super Mario Bros. 3 for the NES is considered to be the best-selling console videogame in history, with sales of 18 million units.
According to NPD Group data, the fastest-selling Xbox 360 title to date is Gears of War, with 1.8 million units sold in the first two months. Madden NFL '08 has sold nearly 897,000 units in its first month.