Nielsen has released its official top ten most popular PC games in the United States for 2008. Nielsen uses their GamePlay Metrics system for determining the games on the list, which polls approximately 33,000 people across the country.

Pos. / Title / Release Year / Avg Minutes Per Week

1. World of Warcraft (2004) – 671 Avg Minutes
2. Call of Duty 4: Modern Warfare (2007) – 403 Avg Minutes
3. Halo: Combat Evolved (2003) – 295 Avg Minutes
4. The Sims (2000) – 213 Avg Minutes
5. The Sims 2 (2004) – 291 Avg Minutes
6. RuneScape (2001) – 451 Avg Minutes
7. Diablo II (2000) – 313 Avg Minutes
8. Team Fortress 2 (2007) – 371 Avg Minutes
9. Counter-Strike (2000) – 282 Avg Minutes
10. Counter-Strike: Source (2004) – 426 Avg Minutes

Via Nielsen