Pros: Character development, great role-playing features, not linear, the first 4-5 hours are beyond epic
Cons: AI is quite dumb, side quests get boring and repetitive, no anti-aliasing
If you begin the series with Mass Effect 2 or Mass Effect 3, then you're a moron. Mass Effect is very innovative in the sense that you can import your save to the next game, so that your decisions will stick. Decisions in this series aren't small and drastically affect how certain things play out. This is a character driven series, designed to play with your emotions and really stay in your mind. Few games do this successfully and have this kind of power; from my experience only a fellow Bioware series does this, Dragon Age, and Dragon Age Origins does an even better job at this than Mass Effect.
But in conclusion, ME1 is a brilliant start to a very well known series. Play this, then play the second, and play the third. Remember to import your saves to the next games, it is critical.