Why is Halo 3 the most popular?

The game was not only a critical and commercial success but taken as a whole, it still stands as the pinnacle of the series. Halo 3 delivered the best overall representation of the Halo experience: an epic campaign with high production values; fluid first-person shooter gameplay; a deep and robust online experience.

When was Halo 3 most popular?

2007 By November 30, 2007, Halo 3 had sold 5 million copies worldwide, and as of that point, was the best-selling video game of 2007 in the U.S., even though the game is only available on one console. On January 3, 2008, Microsoft announced that Halo 3 had sold 8.1 million copies.