The first Mass Effect had issues which dragged down what could have been one of the best Sci-Fi RPGs out on the market. Most noticeable where the combat, frame-rate and dull mission structure. Bioware have made sure that the feedback they received has been address these issues but they have added to the detail and depth of back-story and history of the universe that you will find it hard to put down the controller, even after 30 hours of playing it.
Mass Effect had a great concept that was backed with interesting characters that made the whole experience feel like a living universe that did not shy away from taking concepts found in other Sci-Fi properties and working it into their own fiction. The sequel not only delivers a dark seconded chapter of the trilogy but also doubles the amount of characters and sorts out a more seamless experience, thanks to a more structured game.