#1 - Half-Life 2

     
Half-Life 2 is currently the most popular game overall. Released on 2004-11-16

#2 - Portal

     
Portal is currently the 2nd most popular game overall. Released on 2007-10-09

#3 - Portal 2

     
Portal 2 is currently the 3nd most popular game overall. Released on 2011-04-19

#4 - Half-Life

     
Half-Life is currently the 4th most popular game overall. Released on 1998-11-19

#5 - Mass Effect

     
Mass Effect is currently the 5th most popular game overall. Released on 2008-05-28

#6 - Diablo II

     
Diablo II is currently the 6th most popular game overall. Released on 2000-06-29

#7 - The Elder Scrolls V: Skyrim

     
The Elder Scrolls V: Skyrim is currently the 7th most popular game overall. Released on 2011-11-11

#8 - Age of Empires II: The Age of Kings

     
Age of Empires II: The Age of Kings is currently the 8th most popular game overall. Released on 1998-09-30

#9 - BioShock

     
BioShock is currently the 9th most popular game overall. Released on 2007-08-21

#10 - Deus Ex

     
Deus Ex is currently the 10th most popular game overall. Released on 2000-06-26