In it's time it was one of the best games I'd ever played. I played it on medium quality, so it was mostly the atmosphere and music that I really loved. I found the world and characters so intriguing. I haven't played it since the Orange Box, but it's a classic despite the slightly dated graphics. Give it a go.

@C0V3RT: HL1 is still really good and you should play it but if you don't want to or can't, at least read a synopsis of it and then listen to G-man's speech at the end of the game.

The thing that was great about Half-Life 2's gameplay was that it was never "gotta shoot these dudes. gotta shoot THESE dudes" but that every situation you ran in to was like a little combat puzzle. I don't mean "I have to find these car batteries to open up this door" or "I have to find this enemy's weak spot" but each situation was unique in the way it had to be handled, taking into account the environment and what the game gives you, and there was just loads of work put into every encounter. Think back to Ravenholm. You could chop that level up into 20 or so little "areas". These modern military shooters are too much about just shooting. Shoot some people and move on. That severely limits your creativity with what CAN be done in terms of game-content..