Speaking of Valve, who as a general rule is very secretive with its sales figures (especially regarding Steam), the company has released its worldwide lifetime-to-date retail sales (via Gamasutra). Pre-Steam release Half-Life is on top at 9.3 million, followed by Half-Life 2 at 6.5m and Counter-Strike at 4.2m. These figures don't include Steam sales, which CEO Gabe Newell has said he expects to typically surpass retail sales. Full list after the break.
- Half-Life: 9.3 million units
- Half-Life 2: 6.5 million units
- Counter-Strike: 4.2 million units
- The Orange Box: 3 million units
- Counter-Strike Condition Zero: 2.9 million units
- Counter-Strike Source: 2.1 million units
- Half-Life 2 Episode 1: 1.4 million units
- Half-Life Opposing Force: 1.1 million units
- Half-Life Blue Shift: 800,000 units
Source - GMod10 is 2 years old today! [Garry's Blog]
Source - Valve's Lifetime Retail Sales [Gamasutra]

