Best selling PC games list of all time (from wikipedia)
The Sims (16 million shipped) The Sims 2 (13 million) The Sims 2: Pets [expansion pack] (5.6 million) The Sims 2: Seasons [expansion pack] (1 million) World of Warcraft (11.5 million subscribers) World of Warcraft: The Burning Crusade [expansion pack] (3.5 million) World of Warcraft: Wrath of the Lich King [expansion pack] (4 million) StarCraft (11 million) Half-Life (9.3 million) Half-Life: Opposing Force [expansion pack] (1.1 million) Half-Life 2 (6.5 million) Guild Wars (6 million) Myst (6 million) Doom (5 million) Counter-Strike (4.2 million) Cossacks: European Wars (4 million)
As a complete franchise, it they may be up there. However, individually they did not sell in great volumes.
However, I find it hard to believe the the Roller Coaster Tycoon series sole only eight million copies (info. from an un-cited source) as a whole franchise.
