Multiplayer wise, it's too early to answer that. Once they add more playlists, a skill based ranking system, fix issues, and give us more maps....then I will decide. For now, Halo 2 and 3 are still the best Halo games for multiplayer simply because they had so much content in terms of playlists, maps and they were great for competitive gaming.
Why do people hate ODST? Out of the Campaign's I have played, ODST>Reach>3=4>2
That being said, I love all of them. It's just if it were the end of the world, and I could only bring 1 campaign to play for eternity, I would pick in that order. --- Proud Audiophile DAT COMMANDO HELMET: 58/190 Dominion wins