shio on 03 December 2008
Here's a more detailed sales:
Half-Life: 9.3 million units
Half-Life Opposing Force: 1.1 million units
Half-Life Blue Shift: 800,000 units
Counter-Strike: 4.2 million units
Counter-Strike Condition Zero: 2.9 million units
Counter-Strike Source: 2.1 million units
Counter-Strike Xbox Port: 1.5 million units
Half-Life 2: 6.5 million units
Half-Life 2 Episode 1: 1.4 million units
The Orange Box: 3 million units
Keep in mind that these are only retail. I think if they had included Steam sales, this list would blow everyone's minds.
