This is the E3 trailer for Halo 4. The game looks simply incredible. There's a couple things I don't understand about the story, like why are the Covenant still there but I guess 343 will make an explanation for things once the game comes out in November. The gameplay feels like the classic Halo with a lot of changes in the mechanics like sprinting without having to equip an "item" like in Reach, the forerunner's weapons and the HUD.
Graphically, it sounds VERY good and I'm sure the game will be a complete success in both the campaign and multiplayer. Enjoy.