Grand Theft Auto V
14 days 21 hours
Team Fortress 2
4 days 16 hours
Duke Nukem 3D: Megaton Edition
Of course there's no Fallout news.
Fallout bows to Doom in all circumstances. Y'know, respect for your elders (and superiors) and all that.
Where the hell is Doom? (pardon the slight pun) Doom and Doom II are two of the absolute greatest all-around FPS ever, and they're still available.