This is not just another Halo
The Campaign: The story of Halo 4 is a very emotional story, much like ODST, and really focuses on the Chiefs and Cortanas relationship. Halo 4 takes the fiction from the novels and other media and finally brings it all into a game, with the game focusing on the forerunners and Prometheans and less on just the covenant, and allows for a much more enjoyable story. Some of the things you can do in campaign is just amazing and really shows that 343 has listened to the community as they allow you to do things such as flying a pelican, which the community has asked to do for years. All in all 343 has created quite possibly the best campaign in any Halo have really outdone themselves with the campaign.
The Multiplayer: The Multiplayer of Halo 4 is the best multiplayer i have played in years, with a balanced custom loadout system, tons of unlocks, amazing maps, a very well developed map editor, Spartan Ops and a narrative thread through the whole thing, 343 obviously had some ambitious goals for Halo, and they have done them all so well. Some may say that Halo 4 is pretty much just copy off of Call of duty and not really a Halo game, but i wouldn't exactly say that's true and even though they did take a couple of things here and there from Call of duty, i would say they fit well. One thing that really makes me happy is the fact that they added sprint into the base player traits. I've always hated that you're supposed to be this super fast, super athletic soldier but you couldn't sprint, and the addition of it doesn't break the game but just makes it faster paced. They've also added a custom loadout system, which is balanced quite well, although there should be some changes in the future as at the moment, the DMR is the dominant weapon. Now just because they added custom loadouts doesn't mean you can just spawn with anything, but its really just the weapons that you'd vote to start with in previous halo's. You also have access to two "Perks", The tactical Packages and Support Upgrades, which are pretty much perks from Call of duty except less impactful on game play more just about what weapons you usually use. Armor Unlocks are back but this time you don't have to buy them, you just unlock them as you progress through the game or complete challenges called Commendations. To sum it all up this games multiplayer will keep you playing for such a long time, and with the DLC plans and Spartan Ops seasons, i feel like Halo 4 will last a long time.
So to sum it all up, Halo 4 is one of the best games i have played in a long time and is quite possibly the greatest Halo yet, and i feel that after the dissapointment that was Reach, Halo 4 really redeems the franchise and shows that Halo is still relevant.