I actually expected a drunk thread for some reason.
But anyways, I played through the Half Life 1 games for the first time last year, and they were really something. The game had a lot of cool moments and I absolutely loved the atmosphere (especially early in the game). I can't honestly say if I like Half Life 1 or 2 more, but they both were great at what they did.
I think the only thing I didn't like about the game is that it kind of drags on a bit too long sometimes and the marines are cheap bastards.