Martin Sheen's chain-smoking The Illusive Man, and Mass Effect 2's sophisticated narrative, keeps you guessing until the bitter end.
If that were it - if Mass Effect 2 was merely a game packed with improvements to areas where they weren't even needed - we'd feel perfectly satisfied. Everything that was great about the still impressive first game is just as great in the sequel; we've even started taking many of Mass Effect's qualities for granted. The third-person dialogue system, which means you're never sure how Shepard will play out your selected course of action, is a fun game in of itself, but you don't appreciate its nuances until you compare it with first-person dialogue systems in the likes of Fallout 3 and Dragon Age: Origins. The sheer sci-fi cool of it all - from the Vangelis-esque soundtrack to the power wheel "thoom", makes Mass Effect just as much of a geek love in as JJ Abrams' recent Star Trek reboot. The star-studded cast and superb voice-acting is up there with the standard bearers: Uncharted 2 and Grand Theft Auto 4. But that's not enough for BioWare. BioWare has done all of that, and innovated.
The Paragon/Renegade morality system returns, and again it's easy to know what course of action will result in Paragon or Renegade points, but the ramifications of your decisions don't reveal themselves until the game's heart-pounding climax, when Shepard and his or her eclectic team of disturbed soldiers take the fight to the Collectors - Mass Effect 2's evil alien race. You'd be forgiven for forgetting about the big decisions you've made as you near the game's thrilling end, but by the time all is said and done, you won't be able to forget them.
And BioWare's own good work with Dragon Age: Origins has clearly had an impact on Mass Effect 2's development. The new loyalty system ensures you're keeping one eye on your party members as you use the other to do battle with the Geth and the many mercenary gangs that you come up against. The game doesn't force you to spend time and effort trying to earn the respect of your party members, but you get the impression that it'll be in your best interest to do so. Shepard's suicide mission, as BioWare has explained in the run up to release, is one the Commander may not survive. Keeping everyone sweet will at the very least improve your chances.
The loyalty system manifests itself through some of the most memorable quests we've ever experienced in a role-playing game. Each of the ten potential party members has their own unique quest, which, if completed in a certain way, will make them loyal to your cause. These quests make up many of the game's best moments: they're varied, thought provoking, and seriously impact the story. Asari biotic Samara - she of the eye-popping breasts - has perhaps the best one, and made us literally scream out in astonishment at what it asked us to do. Running it a close second is Subject Zero/Jack's return to her childhood home, which sees her face her demons in a terrifying nod to BioShock's best moments. Each loyalty quest is worth your time, not just because you know it'll help you in the long run, but because they're role-playing gold.
Secondly, your team isn't just a bunch of docile automatons that merely exist in isolation on the Normandy. They're interesting, complex, and they talk to each other. At one point we arrived back on the ship to find Cerberus agent Miranda Lawson fighting the tattooed Jack. If we hadn't had our Renegade conversation option available, who knows how that one would have ended? In Mass Effect 2, there are so many resolutions to each dispute that it's seems impossible to replay the game enough to see them all.