Research firm Nielsen has revealed that Halo 4 is 2012's most anticipated Xbox 360 title, lauding Call of Duty: Blacks Ops 2. The developers, 343 Industries, are bringing about changes across campaign and multiplayer.

Here are five reasons why anticipation is high for the blockbuster shooter.

Spartan Ops

Spartan Ops is new to Halo in Halo 4 and is an episodic, cooperative, ongoing mission-based campaign that expands Firefight - built around surviving waves of Covenant - while bringing a focus to the narrative. The first season includes 50 episodes, spread across ten weeks at five episodes a and is free. Each mission lasts for around 15 minutes with an introductory cutscene to set up the mission.

Spartan Ops takes place six months after Halo 4's campaign and allows players to bring Spartans from multiplayer and continue to earn experience.

The returning Master Chief

John, Spartan 117, or Master Chief. Irrespective of the name of mainline Halo games' protagonist, Halo 4 is clearly pitched as the return of Master Chief. Halo 4 takes place four years after Halo 3, which ended by showing the Chief heading towards a then unknown planet (since confirmed to be called Requiem). The Chief faces a new threat on Requiem, so it's going to be interesting to see how he manages the situation.

Cortana's rampancy

Cortana is 8-years old - young in human terms, but for an A.I. she's a year too old. After seven years an A.I. begins to head into rampancy; Cortana, in Halo: Combat Evolved, absorbed a huge amount of information on the Halo rings from Installation 04. This information overload is undoubtedly harmful in the long-run, but the all-important question is will Cortana become a threat to the Chief?

The developers, 343 Industries, reiterated that how Cortana's with the rampancy is a key plot device in Halo 4's campaign.

Neil Davidge

Neil Davidge, of Massive Attack fame, is replacing Bungie's Martin O'Donnell as chief composer for Halo 4. The revealing trailer, earlier in 2012, showed a more electronic and cinematic approach to the soundtrack, which fits in with the Chief being on an unfamiliar planet facing an unknown enemy with new weapons. O'Donnel had built an iconic sound, remixing the Halo theme throughout. Davidge will need to pay homage and live up to the expectations.

Forerunners and Prometheans

Requiem was once home to Forerunners, the creators of the seven Halo rings, but has been uninhabited for millennia. The Flood wiped out the mysterious race but signs of the existence remain in the new enemy class: the Prometheans, a Forerunner A.I.

"I've long dreamt of this day, Reclaimer," the campaign trailer noted as it ended. The voice is unknown, but many have speculated it could be a Forerunner antagonist such as the Didact. Wherever, or whatever, it is, the Covenant won't be the central antagonist in the campaign.

Above are just five points generating excitement for Halo 4. Along with a new graphics engine, an all-star development team - including developers from the 3D Metro Prime games, and Sotaro Tojima, composer on Metal Gear Solid 4: Guns of Patriots - and the radical changes to the multiplayer formula, such as Ordnance Drops, Halo 4 looks genuinely different from Bungie's Halo titles.

Halo 4 releases November 6 on Xbox 360.