Half-Life has been the gold standard for immersive, science-fiction adventure for years. Was one of the only games where the HUD made sense, the main character wasn't some stereotypical action hero, and the story really did make you feel like you were playing a movie.
Mind you this is back when games were still striving for that, before the call of duty days, before the
bullshit.Spoiler
The Ant-lions were probably my favorite part of HL2 (besides the zero point energy weapon, mmmmmmm.) Those prison levels where you get to flush out the combine by using the hormone sacs = win. I only wish they stayed with you the rest of the game.
And the Vortigons referring to Gordon as "the free man" is so good and evokes Dune's Fremen along with every other archetype of the free hero saving the people I can remember.
Bless those games.