22. "Half-Life 2"

Release date: November 16, 2004

Platform: Xbox, Xbox 360, PlayStation 3

Buy it here.

Roughly 20 years after the events of the first game — in which a group of scientists accidentally create an inter-dimensional instability that lets aliens flood the earth — you play one of those scientists, Gordon Freeman, as he collects information and weapons to fight an oppressive multidimensional empire called The Combine. "Half-Life 2" is a first-person shooter that has a lot of fun with physics, exploration, and strategy.