Lots of Halo 3 Beta reviews here - What we've seen is three maps that are unfinished in the game. It looks excellent but in reality this really is the tip of the iceburg as to what Halo 3 is going to be. So, thought I'd hit you with facts of what the story is based on and some of the stuff we'll see in campaign.
Cortana, your AI that jumped aboard your suit in Halo 1 remains trapped in the hive mind of the Flood known as the graveyard. The Elite's, following the event's in Halo 2 have split from the covenenant and allied themselves with the humans. The brutes, now take the elite's place within the covenenant as the guardians of the deranged leaders, the prophets... who want to take the covenant on a 'great journey' by firing the Halo rings which were created by the forerunners to eradicate all living sentient life in the galaxy to kill the flood.
At the end of Halo 2, the master chief is seen entering Earth's orbit in an ancient Forerunner vessel with Earth being overrun by the covenenant. He's their to finish the fight. The Halo rings around the galaxy have been primed and are ready to fire destroying all life in the galaxy.
The covenant are at Earth to find something ancient and Forerunner buried deep beneath the sands of Africa.
So, the game will have on line Co-op and will take in loads of environments. Including Halo rings, Desert Earth, Inside of ships and snow bound missions. There are new vehicles including a snow mobile. New weapons, such as a spartan laser.
Why is Halo so big... It's the story... It will be like controlling a blockbuster movie and the developers at bungie are confident that this will be the best looking game on Xbox.
Will it live up to the hype - I hope so. The multiplayer is excellent but the campaign story mode is where halo needs to be outstanding.