Yeah, I'd have to say that no game rivals any of the HL games for me. I love these games, and enjoy them, far more than any other game.
I remember counting down the days till this was released. Didn't have enough money to buy it on launch, and purposefully stayed away from any thread that might have spoilers in it. Got the game as a Christmas gift and spent the entire next day or so playing it.
I also remember that, at that time, this was the only game my brand-new GFFX 5950U couldn't run 100% maxed (including AA). I was blown away by the graphics.
Man that was a lot of fun.
Really getting stoked about EP3.