What I loved about Halo was the story, because every FPS boils down to the same kind of multiplayer death match. Camping, sniping etc. Halo 3 ended the series in god awful fashion. I was super bummed about the ending. I sold all my copies of Halo in favor of Modern Warfare. Those stories were AWESOME and the missions were great. The multiplayer is great too, because there is incentive to keep playing. There was good closure at the end.
Dont get me wrong, I was obsessed with the first halo, co op, everything was great, Halo 2 wasnt bad, had some innovative things, and Halo 3 was just eye candy. I was so pissed at the ending.
I dont even know if ODST or Reach even have stories...