Cool story bro, you want a cookie?
Just about every thread imaginable where people have the choice of saying their favorite popular game they hate you get about 10 people that say "Man, Half Life is such an overrated piece of garbage. I'm so glad I'm cool enough to see past its generic scripted bullshit" so excuse me if I come off a bit harsh.
It came out in 2004, as far as shooters in 2004 go, it was pretty damn amazing to say the least. Also it was very sandboxy in its combat. As in, some jackass script didn't hold your hand telling you who to shoot, how to shoot them, or when to shoot them. Its very much like Halo in that regards. Halo was "run and gun" and yet it gets even more praise despite being even more lacking. The gravity gun added a whole new level of depth to the combat (as it gave you a lot of options) but in the end its still combat. All shooters involve shooting of some kind.
Also the beautiful environments, seemlessly integrated script pieces and story, nice vehicle sections, and physics puzzles. It had a lot to offer that most games these days don't have. I think it still holds up to today, because we still have a lack of strong fps games as far as the single player goes. Bioshock and Crysis are the only 2 I can think of (portal is a physics game, not a shooter).
I find it fun, other people find it fun, and if you find it fun then why do you care if it lived up to the hype is got? Does that diminish your fun somehow?