I'm not much of a console gamer--not for any snobby, elitiest reason, just practicality and economics--but of the games I've played on the PC in this generation, most were I think cross platform.
So in no particular order:
Mass Effect Trilogy
Portal 1 & 2
Half-Life 2 + Episodes 1 & 2 (where oh where is HL3!!??)
The Walking Dead
Dragon Age Origins
Saints Row 2
Batman: Arkham Asylum
X-Com: Enemy Unknown
Beyond Good and Evil HD (if that counts!)
Honourable mentions include the Crystal Dynamics Tomb Raider games Legends, Anniversary & Underworld (haven't played the new one yet), Ghostbusters: The Video Game, Journey, Kerbal Space Program, the WH40K Dawn of War games and Left 4 Dead.
Deus Ex: HR, Arkham City and Assassin's Creed 2 should probably be in there somewhere too, but I've yet to finish these, so I can't really rate them fairly.