Valve's Steam service took in almost $1 billion USD, according to Forecasting and Analyzing Digital Entertainment, where they say: "Estimated revenues through the major digital PC retailer were estimated at $970 million USD in 2010, with December capping off the year with an estimated $213 million USD." They offer a list of the top titles on the service, which was dominated by shooters:

Top Selling Titles, by Estimated Gross Revenues in 2010

• Call of Duty: Black Ops (Activision) - $98.2 Million USD
• Call of Duty: Modern Warfare 2 (Activision) - $39.4 Million USD
• Left 4 Dead 2 (Valve) - $36.0 Million USD
• Battlefield: Bad Company 2 (Electronic Arts) - $25.4 Million USD
• Sid Meier's Civilization V (2K Games) - $21.9 Million USD
• Portal (Valve) - $20.0 Million USD
• Fallout: New Vegas (Bethesda Softworks) - $17.0 Million USD
• Metro 2033 (THQ) - $13.4 Million USD
• Mafia II (2K Games) - $11.9 Million USD
• Warhammer 40,000: Dawn of War II: Chaos Rising (THQ) - $10.8 Million USD