Cute
Explain it to me then.
Amazing graphics on a technical level (It's why everyone seems to be shocked at how good it looks)
Artistically, the atmosphere, the lighting, the colours are all spectacular (evokes Metroid Prime)
The Story is completely new and hitting notes never done before (Cortana's Rampancy, Forerunners)
Brand new enemy and style (The covenant took up about 7 seconds of gameplay and the elite got disintegrated)
New Weapons and animations
Fantastic Sound Design and great music giving everyone the chills as Cortana's going nuts
Basically EVERYTHING being completely new and different. That's what you're missing.
Now you might respond and try to clarify but don't really bother. If you're so blind and ignorant as to think this looks like "every other Halo" then you have absolutely no perspective of what Halo is.