I can't speak for everyone, but I didn't like Reach because all the things I liked about previous Halo games was missing, replaced by all the things I didn't like about them, plus a few more for good measure. It was experimental, in a way. I didn't like it, but I"m glad they at least tried something new.
It's time to kick ass and chew bubblegum, and I'm all out of gum
ODST had the best music, a decent campaign, a decent story, decent dialogue/characters, Firefight, and Halo 3's matchmaking. Halo: Reach had decent music, a decent campaing, a decent story, mediocre dialogue/characters, and Halo: Reach's matchmaking.