Pros: Graphics, Storyline
Cons: Glitching, Collison
The bottom line: Buy- It's worth it.
Mass Effect, to say the least, is definitely one of the games I have netted the most time playing on my Xbox 360. First, you get to start off by naming your character(______ Shepard), followed by designing his/her physical appearance and class. The opening scene is tailored to your class setting, so it could be different depending on how your character is specified.
Once you start playing the game, you discover that you are on basically a giant space cruiser which is owned by humans and is operated in an effort to prove the human race's worth to a giant council of alien races, all of whom have these elite soldiers called Spectres.

I could go on and on explaining the plot to you, but believe me, IT IS WORTH IT TO READ THE BOOK BEFORE PLAYING if possible. Many of these alien races are explained/introduced, and the plot for the game is set.

That being said, I can conclude by saying that the graphics of Mass Effect are VERY decent, but occasionally suffers from camera problems and collison glitches (at one point I got caught in the galaxy map). These problems rarely occur, however and do not usually detract from the main game.

I would also like to say that this game IS worth playing more than once. This is like a giant tree with all of your actions having different consquences on your story. The ending is great too.