Still, that level where you enabled the Sentry Bot and went to town with the big boys was probably about the best gaming moment I can remember. That's what killed me about that game. You had some amazing immersive scripted moments (they stole my baby!), but none of the memorable parts had anything to do with combat after the first hour or so.
HL2 I'm not quite done with. I loved the airboat, not loving the buggy nearly as much. Overall I think the level design is absolutely amazing, the enemies are tons of fun, and the pacing is well thought out, and the dialogue has made me laugh a few times. The boat level, the one everyone said was too long, felt right to me. The buggy level, which previewers wet themselves, feels long already and I'm just starting. Getting out to flip it while being attacked isn't as much fun as I would have hoped.
Halo 2 had the same problem of every room looking the same, but it had the most memorable combat moments of any game I've played. I didn't expect to like the game, but wow. There were so many times that I died, reloaded, and tried to compensate for how they killed me, only to have the aliens sneak up on me in a new way. The AI might not have been bright, necessarily, but it was very varied. Most importantly you fought actual battles.
In retrospect I should give Halo more credit for that - it let you see the AI. In Doom 3 AI was not needed. Something showed up - you killed in. In HL2 thus far it seems similar, only the AI has better ways to show up (admittedly I'm early in, spent most of my time against zombies, and adore the fact that when I duck behind a door to reload the Combine seeks new cover, so when I look back in I waste time finding them again). Halo 2 had moments of larger firefights. You're running around chasing them or they're running around chasing you. You had lots of time to see the AI in action. Much more than the original HL, where everyone discussed how wonderful the AI was but more often than not I'd see the soldiers and kill them in the same few seconds.
Hmm. I guess I respect the Halo shield system much more now.