Brought to you by the creators of Knights of the Old Republic and Jade Empire, Mass Effect is the spiritual successor to those games. Which is a very good thing, as its precursors were both excellent. Mass Effect continues the trend.
Assuming the role of Commander Shephard, the first human Spectre (a kind of galactic superspy with a license to do whatever they want in the name of galactic security), you are tasked with hunting down Saren, a Spectre who has gone rogue. What follows is an epic, exceedingly well-written sci-fi tale that has you traversing almost half the Milky Way in your quest to bring Saren to justice.
Mass Effect possesses high quality graphics that truly convey a sense of exploration. High-tech space stations and ships glow luminously and barren planets are windy and dust-choked. The character models are very realistic looking, mostly because of their flaws; their scars and somewhat asymetrical features give them a sense of personality. Unfortunately, there is significant texture pop-in when loading or entering a new area, but not enough to mar the experience. Soundwise, the voice acting is top notch, with stars such as Keith David and Seth Green delivering great performances. The music is somewhat subdued, but solid, and it sets the mood well.
Mass Effect is a long game, but you'll be too busy having fun to notice. The battle system has a steep learning curve, but, once you get the hang of it, proves to be very versatile and entertaining. There are numerous sidequests and uncharted worlds to explore; you will never lack for something to do. Factor in multiple endings, character types, and a New Game+ feature, and you have a winner on your hands. Highly recommended.