Half Life

I had given up on video games by college, and all though I had grown up on Atari and C64,  I didn't feel like the medium would be worth anything for a long time.  The technology sea-change for me, was a little Sci-fi adventure/thriller called Half Life.

Though you spend most of your time delivering shotgun blasts to alien zombies, Half Life really transcends reaction-time-based-gameplay by injecting a massive amount of story and atmosphere.  Here are some artist concepts (mixed from the whole series) to hopefully wet your appetite:

Half Life 1 was released around 1998, the second, 2004.  There have been 4-5 other add-on games that fill in the story gaps of the larger pieces.  If you ever wanted to check this great game out, you'd be okay to jump in anywhere, without being in the dark.