Probably going to get a few flamethrowers aimed at me for this, but meh.
Hl² was one of the most mind-numbingly boring experiences I've ever come across.
In the first half hour, the only thing that happened was me tossing a can into a bin. Sure, it's a tutorial... but in that half hour, I had 4 loading times of at least 2 minutes, one of which was in the middle of a chase (the apartment thing). No, my computer doesn't suck, as I can play the game on max settings, but I don't even do that.
Even when the actual FPS-part starts, it's just plain boring. Go through a tunnel, kill guys, go to the next tunnel.
Puzzling isn't that awesome either, you basically pick up stuff and drop it elsewhere, then jump on it. How innovative... for about 10 seconds. Then the next 2 minute loading time starts.
And the entire atmosphere/world isn't immersive at all, to me at least... maybe it's because there's those loading times every 8 minutes of actual gameplay.
Boring.