26 games have a developer similar to 'Valve'
(PC) Counter Strike: Source
(PC) Counter-Strike: Condition Zero
(XBX) Counterstrike
(PC) Day of Defeat: Source
(PCD) Day of Defeat: Source
(PC) Deathmatch Classic
(PC) Half-Life
(DC) Half-Life
(PC) Half-Life 1 Anthology
(PC) Half-Life 2
(PCD) Half-Life 2
(PC) Half-Life 2: Episode One
(PCD) Half-Life 2: Episode One
(PCD) Half-Life 2: Episode Two
(PC) Half-Life Counter-Strike
(PC) Half-Life: Day of Defeat
(PC) Half-Life: Game Of The Year Edition
(PC) Half-Life: Valve Premier Pack
(PCD) Portal
(PC) Ricochet
(PCD) Team Fortress 2
(PC) Team Fortress Classic
(PC) The Orange Box
(360) The Orange Box
(PS3) The Orange Box
(PC) Worldcraft 1.6