I never played Halo 2 but I HATED Halo 1. Thought it was the most overrated game of all time. Ugly, outdated graphics, super seriously repetitive level design, simplistic plot (people keep saying that the Halo games have good stories, but I don't understand how), annoying Cortana voice overs, seriously repetitive level design, cliche after cliche, only 5 or so types of enemies, seriously repetive level design (wait, haven't I been in the EXACT SAME AREA like 3 times already before?), laughably bad dialogue, etc. etc. etc. It only got a lot of buzz because it was the first original FPS on a console that wasn't totally unplayable and got a lot of marketing hype.
I do love Red Vs. Blue though.
I'm not a fan of Half-Life 2 either though--again, there's no plot. "Okay, let's go here and blow this up. Now we're going here and getting this cool new weapon that shows off our physics programming abilities! Now we're going here to blow this up, but first we need to go through here and kill these zombies...and now we're going here to blow this up...and LOOK! THE G-MAN IS BACK, and as always, he's talking nonsense! Roll credits! WOW! Brilliant! I can't wait to find out what happens...or what just did happen...or really what the hell any of this is all about. Hmm. Hey, didn't this same thing happen with F.E.A.R.?"