Holy Etruscan knoods, Batman, this games sets a new standard for ingenious dialogue and immersive environments! Attempting to quantify Mass Effect 2's multifold complexity would be a disservice, so I'll skip it. The branching dialogue offers so much variety that you could never experience the same playthrough twice.
There's a lot to do in Mass Effect 2. You have to pick up the pieces from the first chapter, in which you halted the incursion of a machine death god, and investigate what is causing human colonies to vanish. Hopping around the galaxy in a souped-up, top-of-the-line spaceship, there are many, many planets to visit, each rich in minerals and metals, populated with different races, and teeming with storylines galore. To say that you could spend a lifetime exploring this game is an understatement. Unlike most games where this is a horrifying prospect, the incredible writers make this akin to reading a fine novel, one in which you choose your own adventure. Mass Effect 2 is fun, engaging, and blazes new trails for immersive gameplay.