Today I finished Halo 2! Liked it, but overall I liked Halo CE more (except for the last two levels that I found very frustrating in CE).
I mean, there are some things that Halo 2 does better imo: like more variety in the level design, the possibility to carry 2 guns, to play as the Arbiter, and better story telling and character presentation! But still, the gameplay and shooting itself was way better in CE, imho!
In Halo CE I had the impression the enemies were overall better placed in the areas so you could plan a lot better your tacts, also the levels were more open. And the flood: in Halo 2 they were extremely boring to fight against and I had the impression that almost any weapon was pretty weak agains them, even the shotgun! While in Halo CE you could oblitarate then with some weapons, specially the shotgun, and plan better your approach!
I have just started Halo 3 and am loving it. I'm having the CE vibe, what is great! But I hope it keep up the good pace till the end, and hopefully the flood will not be as frustrating as they were in Halo 2.
Really great serie so far! Loving it!!