Ok, lets do something, not too long ago, steam was going to have every game ever, so, lets compile a list of every pc game ever. ONE game each, ready? I'll start:

Half life

Doom.

Just by the way, as emulators are possible for the PC, does that mean that technically every game ever would be 'on' the PC?

mech-commander

That's impossible. This is the best I could find on Wikipedia http://en.wikipedia.org/wiki/List_of_MS-DOS_games http://en.wikipedia.org/wiki/List_of_Games_for_Windows_titles

If a list isn't on wikipedia, it is safe to assume it does not exist.
Oh and back to the game: Halo

This thread is uninspired. But hey, who am I to judge?

Postal 2

Hitman Blood money, friggin awesomeness in a box