4.50 Left 4 Dead 2 (2009)
4.32 Half-Life 2: Episode Two (2007)
4.20 Portal (2007)
4.15 Left 4 Dead (2008)
4.10 Half-Life (1998)
4.08 Half-Life 2: Episode One (2006)
4.02 The Orange Box (2007)
3.94 Half-Life 2 (2004)
3.91 Counter-Strike: Source (2004)
3.65 Half-Life: Opposing Force (1999)
3.61 Half-Life (Game of the Year Edition) (1999)
3.51 Half-Life: Blue Shift (2001)
3.34 Half-Life (2001)

^*Games must have at least 5 votes to be included.