For me it would either be Halo 1 or 2, or Bioshock.

I can't really think of many others besides the two you mentioned in terms of new games.

There's Perfect Dark, Doom, Duke Nukem and Marathon which are great classic games, but I'm not sure if the population is there at all, it's been a while since I've played them.

I played Team Fortress 2 on a Macbook Pro trackpad for about a year, it was a horrifying experience.

Slender is dread inducing, and Amnesia I couldn't play more than an hour before I said "Nope."

But if we're talking 360 games, then Dead Space would take it.