We already know that PC game sales in the United States fell 14 percent in 2008 to $701 million, according to figures by research firm NPD, but those numbers do not take into account sales via digital distribution methods or subscription fees. Bearing that in mind, NPD has now released a list of the best selling PC games in those retail stores, giving us a general sense of some of the most popular titles of 2008.

Activision Blizzard clearly dominates the scene with nine titles in the top 20 including the best selling PC game of the year, World of Warcraft: Wrath of the Lich King, while EA’s highly anticipated Spore managed to occupy the second slot despite piracy and the SecuROM fiasco. Meanwhile, Valve’s Left 4 Dead and the Orange box took the 18 and 20 spots respectively, but would have probably been much higher up the list if digital downloads via Steam were tracked. Check out the full list after the jump.

1. World of Warcraft: Wrath of the Lich King - Blizzard
2. Spore - Electronic Arts
3. World of Warcraft: Battle Chest - Blizzard
4. Age of Conan: Hyborian Adventures - Funcom/Eidos
5. Warhammer Online: Age Of Reckoning - Mythic/EA
6. Call Of Duty 4: Modern Warfare - Activision
7. The Sims 2 Double Deluxe - Electronic Arts
8. World Of Warcraft: Wrath of the Lich King Collector's Edition - Blizzard
9. Fallout 3 - Bethesda Softworks
10. World Of Warcraft: Burning Crusade - Blizzard
11. Call Of Duty: World At War - Activision
12. The Sims 2 FreeTime - Electronic Arts
13. World Of Warcraft - Blizzard
14. Sins Of A Solar Empire - Ironclad Games/Stardock
15. Warcraft III Battle Chest - Blizzard
16. The Sims 2 Apartment Life - Electronic Arts
17. Crysis - Crytek/EA
18. Left 4 Dead - Valve
19. Diablo Battle Chest - Blizzard
20. The Orange Box - Valve