There are notable downsides to going episodic with video games. Players, who have been trained to expect 20 to 60 hours of gameplay per title, might reject the model, even though it's lower priced. Critics tend to penalize episodic games because of their length. And retailers don't quite know how to handle the games.

Because the average title sells for $50 or $60 these days, a new game carrying a $20 price tag can make the others seem overpriced. $20 is typically bargain bin pricing for games - and stores are still trying to figure out how to position them.

Online services like Steam and Xbox Live Marketplace, help supplement sales, but Newell said the majority of all sales still come from retailers - even on episodic content. (It's not just "Half-Life," either. Valve worked with Texas developer Ritual to distribute "SiN: Episodes - Emergence" earlier this year. A second installment is due soon.