The Entertainment Software Association has highlighted new NPD data on the PC game market, following full-year analysis on the $18.85 billion dollar video game industry pertaining specifically to PC software sales.

Computer retail game sales in the United States totaled $910.7 million, or 36.4 million units, a decrease over last year's results, when PC games sold in a retail setting saw revenue of $970 million.

Following the ESA-trailed results, NPD released the top 10 best-selling PC games of 2007 to online outlets including Worlds in Motion sister site Gamasutra, revealing two major franchises - Vivendi/Blizzard's World Of Warcraft and Electronic Arts' The Sims - dominating much of the charts. The full run-down is as follows:

1. World Of Warcraft: The Burning Crusade (Vivendi) - 2.25 million
2. World Of Warcraft (Vivendi) - 914,000
3. The Sims 2: Seasons Expansion Pack (Electronic Arts) - 433,000
4. Call Of Duty 4: Modern Warfare (Activision) - 383,000
5. Command & Conquer 3: Tiberium Wars (Electronic Arts) - 343,000
6. Sim City 4 Deluxe (Electronic Arts) - 284,000
7. The Sims 2 (Electronic Arts) - 281,000
8. The Sims 2: Bon Voyage Expansion Pack (Electronic Arts) - 271,000
9. Age Of Empires III (Microsoft) - 259,000
10. The Sims 2: Pets Expansion Pack (Electronic Arts) - 236,000

However, digital downloads were not factored in to the NPD data, since the firm only tracks bricks-and-mortar retail sales currently, making it difficult to track exactly how the PC market is trending as a whole with the rise of casual games and even digital downloads for more 'hardcore' titles.

How would the PC market's revenues shape up if microtransactions and other predominating business models were factored in? It's hard to imagine that we won't at least have a better idea of this next year. And yet it's worth pointing out, on the other hand, the number one item of PC software, Warcraft, which is the industry's killer app with a recently-announced 10 million users, is a subscription-based retail title -- a business model lots of people think may be on the outs with the advent of free-to-play and RMTs. Go figure.