I wanted to make this review short, but it's hard to stop writing, even when excluding facts that could potentially contaminate an exceptionally well thought-out gaming experience. There's just so much to say. Half-Life 2 is simply, the best single-player shooter ever released for the PC. It does so many things right in so many ways that it might be possible to write a thesis on the topic of Half-Life 2 compared to other single player shooters.
What Valve has created is simply a masterpiece, a work of art in the genre. Not only does it engage the mind with mysterious happenings, vagaries, and mostly intelligent dialogue, but also captures the senses with an awesome visual style made possible by well thoughtout technology. Once the initial shock of it all wears off and it becomes possible to peel back the polished layers of sight and sound, there is an excellent shooter here.
Half-Life 2 doesn't do anything particularly new; it doesn't really innovate in many ways. But what it does is set a new height for all other designers of first-person shooters to reach. It still isn't exactly perfect, but it's about as close as I've seen.