Stellar Bioware's space-opera in RPG form is, on the whole, a magnificent piece of storytelling and a thoroughly absorbing, playable and re-playable game that goes out of its way to accommodate newcomers to the genre but doesn't lack depth. Here I'll concentrate on the more 'filmic' qualities of Mass Effect, on the assumption that if you want a review that focuses on gameplay you'll go to a gaming website. Suffice to say I've enjoyed playing it through multiple times (on the PC); one could pick holes in various bits of the implementation, such as the AI in combat and the inventory system, but the strengths far outweigh the weaknesses in gameplay terms.
Mass Effect is, up to a point, what you make it. Commander Shepherd, the protagonist, can be selfless, principled even to the point of being holier-than-thou, or unsentimentally pragmatic; he/she can explore the blurry boundary between patriotism and xenophobia, or hold out for species-blindness; there are politicians to be mollified, tolerated or deliberately alienated, as well as a crew representing five different species, none of them straightforward quasi-racial caricatures, whose inner lives Shepherd can discover (or not), sympathize with or mock. He/she may find herself falling for one or two of them, but there are also sacrifices to be made. It's testimony to the quality of the writing, character design and animation and (not least) voice acting, that most of this feels supremely persuasive. One can feel really guilty about some of the choices one's forced into.
Technically, the game is often miraculous. Something it manages really well is the focus on nuances of character, helped along by a magnificent facial animation system, and some first-rate voice acting in most of the primary roles. Special nods go to the always excellent but never better Jennifer Hale as the female Shepherd; lovely, characterful work from Raphael Sbarge (Alenko), Kimberly Brooks (Ashley) and Brandon Keener (Garrus), and a fine performance from Fred Tatasciore as Saren, no one-dimensional villain. Not all the squad-mates are as well-written or performed, and neither Tali nor Liara quite comes to life as a character; their line readings tend to sound less spontaneous, but the actresses really do have much less to work with. (Edit: but Liz Sroka is quite wonderful in Mass Effect 2, given much better material and delivering it with terrific dramatic power.)
There are limits and compromises to the game's self-conscious feminism: when the female characters aren't tough soldiers they tend to be a bit feeble, and the exploitative character design for Matriarch Benezia should have been sent back to the drawing board (she's voiced by an uncomfortable-sounding Marina Sirtis). On the plus side, supremely solid support comes from the likes of Keith David as the compassionate, experienced Captain Anderson, and the unmistakable voice of Seth Green is very well cast as Joker. He gives a subtle, variegated performance that steals a few scenes without ever seeming to be doing so on purpose.
There are two fundamental tensions which Mass Effect has to disguise, if we're to suspend disbelief. The first and less important is pacing. In a race against time to save all civilization from an ancient foe, there's always time for a long chat, a side quest, a shopping trip. I'm happy to accept that as a necessary fudge; it's the price you pay for replayability. More serious is the tension between choice and linearity. For all the nuance with which you can create and develop 'your' Commander Shepherd, you gradually discover on multiple playthroughs that most of your choices are less meaningful than you think. Whatever you choose, the consequences are much the same in terms of plotting, and have only limited ramifications at the level of personal relationships.
This is one of those moments where a technical necessity starts to become a philosophical tenet by accident. Mass Effect presents itself as a morality, a story about choices and their consequences, but the more you play the game, the more you become aware that those consequences are locked down in advance. Of course they are: just imagine the inefficiency otherwise - the amount of dialogue, cut-scenes, character relations and plot developments that would branch off. Mass Effect simultaneously flatters and explodes the heroic illusion that every choice one makes changes the universe. That at least is a provisional conclusion: it'll be very interesting to see how, and how far, the sequels work out the consequences of choices made in the first game. And I for one will certainly be playing.