By Alfred Hermida
Technology editor, BBC News website
Halo was the game that anyone with an Xbox had to have. Widely acclaimed when it come out in 2001, it went on to sell more than five million copies worldwide.
Halo 2 features new weapons such as an energy sword
It was one of those games that took on a life beyond the confines of the console, spawning a legion of devoted disciples.
Three years on, with expectations at fever pitch, the pressure is on game developers Bungie to deliver a masterpiece.
Fortunately Halo 2 largely lives up to the hype. Bungie has taken all that was great about the original and gone one better, to produce a polished and accomplished first-person shooter.
Weapons at the ready
The first thing that hits you is the look of the game, with a Halo universe full of detail, with crisp and sharp alien environments.
At times, though, the design of these worlds is indistinctive and confusing, leaving a player wondering which is the way ahead.
Picking up the game is like getting reacquainted with an old friend. The controls are as intuitive as ever, but they are now much more responsive.
Levels load virtually seamlessly and progress is saved automatically at regular checkpoints.
The look of the game has improved greatly
One major change widely reported is the ability to fire two weapons at the same time.
This is not simply a novelty. It is integral to the game and adds a degree of extra complexity to the gameplay.
It forces choices that could mean the difference between blasting through a level or struggling to stay in the game.
The dual-weapon wielding also adds to the longevity of the game, levels can be played with different combinations of weapons.
The story behind Halo 2 has been shrouded in secrecy. At the end of the first game, the hero, Master Chief, had defeated the alien race, the Covenant and destroyed Halo, a weapon of mass destruction.
This time round, the alien enemies are taking the battle to Earth. But that is only the beginning of the adventure.
The plot is integral to the game and there are twists to keep gamers guessing.
Given that you are playing out a pre-determined plot, the game is inevitably a linear adventure.
Cutscenes fill in the detail and sometimes the dialogue tends to sound bombastic and laboured.
Enduring appeal: 10
Bungie has been able to throw in a wide range of fighting styles to keep gamers hooked.
The action swings from close quarters intense shootouts, to long-distance sniping, to no-holds barred explosive fun in a tank.
The only downside here is the AI of Halo 2. It fails to live up to the rest of game.
Enemies shelter if they come under fire, but too often they just crouch behind cover, making it easy to sneak up and shoot them.
One of the biggest limitations of the original game was the inability to play online.
Fans found ways around this using a PC and a home network. But it was never a very satisfactory experience.
This time round, Bungie has invested time and resources into taking the game online.
Halo 2 can be connected to Microsoft's subscription-based broadband network, Xbox Live.
It comes with a party system, which means a group of friends can move game to game online as a group.
Gamers can create their own team or compare online ratings against others.
Bungie has thrown in several game modes, which add a degree of variety missing from most other online shooters.
The ability to play online will no doubt tempt some to take the plunge into broadband.
It is also likely to keep players coming back to the game, even once they have saved the Earth.
Halo 2 has the feel of an instant classic, with stunning graphics, addictive action and a compelling plot.
Halo 2 is out on 9 November in the US and 11 November in the UK