My thoughts what halo done great at

Halo:CE - most fun singleplayer

Halo 2 - Best story + lore + Easter Eggs

Halo 3 - Best Multiplayer

Halo 3: ODST - Best atmosphere + Co-op

Halo: Reach - Best “next step” to the halo gameplays + uniqueness + best armors

Halo 4 - Best…uh…I’ll get to that

Halo: MCC - Best damn graphics I’ve seen + forge evolving

Halo 5: Guardians - Best worst story, Best gunplay