Best games in Halo franchise:
Halo CE, Halo: Reach.
Yea I was confused at the start too but this is not supposed to be Halo 4. That will probably be the Halo Chronicles thing. This is a prequel that will probably be much different than the Halo Trilogy.
It looks to be a MMO in first person that comes with customization different classes, etc or maybe something like a multiplayer only online game with the same things in mind.