scottie on 06 August 2009
S.T.A.L.K.E.R.: 2.000.000 copies sold
3 September 2008 Shadow of Chernobyl, Clear Sky
GSC Game World announces its S.T.A.L.K.E.R.: Shadow of Chernobyl has sold 1 million copies worldwide and 1 million licensed copies in ex-USSR countries.
"We are very pleased that S.T.A.L.K.E.R. became so popular among players from all over the world, - said GSC Game World CEO Sergiy Grygorovych. – S.T.A.L.K.E.R. is more than just a game now. Financial success will allow us to develop S.T.A.L.K.E.R. in different directions as a brand."
http://www.stalker-game.com/en/?page=archive_news&subpage=3
As for CoD4 PC sales, it's very hard to ignore official activision press reports
