Half-Life 2
Half-Life 2 is a very impressive and engaging shooter, and a faithful follow-up to one of the greatest PC games of all time.
Doom 3
While not as remarkable as the technology that fuels it, the game itself is put together well enough to make Doom 3 legitimately great, all things considered.
Jedi Academy
It manages to take all the fun parts from its predecessor and greatly expands them to create an engaging, new action game in its own right.
