Halo 2 > Halo 3 > Halo 3 ODST > Halo Reach > Halo CE
Based on campaigns.
Halo CE
Best mission: Silent Cartographer. One of the few missions from this game that has replay quality
Worst mission: Hard to say, either Halo, 343 GS, The Library, Keyes, or The Maw, all were equally as boring and unplayable
Halo 2
Best mission: Uprising, extracting revenge on the brutes is just epic, plus I loved the elite and grunt allies.
Worst mission: Sacred Icon, an entire mission of flood and sentinels doesn't do it for me
Halo 3
Best mission: The Storm, it's so fun just advancing through the factory just killing covenant
Worst mission: Tsavo Highway, it was alright, but it just seems an unnecessary mission, not much happens in it
Halo 3 ODST
Best mission: ONI Alpha Site, the beginning is just epic, retreating along a bridge while an unstoppable covenant army advances towards you
Worst mission: Probably Kizingo Boulevard, although it is a lot more fun in a wraith
Halo Reach
Best mission: Exodus, I liked the city environment, and a nice break from those darn elites
Worst mission: LNoS or Nightfall, just bored me