Out of all of the Halo series, they really put a lot of fan service into this game. Customizations was on par. To date, I don't believe another Halo game has came close.
Story was different and refreshing. It put the player at the center is the much before unknown world of Reach. It took is upfront and personal with the major loss we are only hinted at in Halo: Combat Evolved.
This new technique and point of view was amazingly refreshing. The game suffers from changings to the armor abilities of a past tense when all of the future games never had these abilities. It sort of rewrites history that way. Introducing something that the Master Chief himself couldn't do? Why? but in the end the story speaks for its self. Bringing you the player face to face with Pillar of Autumn. Man that was an exciting moment.
That ending, playing your death, watching you fail. The screen breaking and cracking. The best death in a Halo game to date.