I played through HL2 in a marathon session (interruped only by lunch with friends), then went on to VTM Bloodlines. That got replayed quite quickly, and turned out to be a very different experience (went from a Ventrue to a Malkavian). After that, playing through HL2 again wasn't as stunning of an experience. Still, it was a great game, just because it's presented so stunningly well. The physics, while cool, weren't as terribly revolutionary as Valve seemed to be playing, but they're still fun to play around with (especially if you turn on sv_cheats and try host_timescale 0.4). Hopefully they'll push future FPSes towards the same thing (like the 'grass' and 'helmets you can shoot off' trends), and we'll see some truly interesting uses of physics in the next few years.
As for this game, while I can't say I've been eagerly anticipating it, the Xbox reviews were uniformly good, so hopefully it made the transition to a proper platform for FPSes well.