Darksiders II is out for free on XboxLive. Do I need to play Darksiders to understand whats going on? Or is the game completely different to the first?
31 Answer
Even though there a ton of references to the first game in the second one, there is no information from game 1 that you need to understand game 2. You play with a different horseman (death) and your quest is about finding out wtf happened to war (the horseman from 1). I would recommend playing the first one first, because it's awesome and it will give you better incentive to play through 2, but it's not necessary.
Here is a better explanation, but with spoilers:
In Darksiders 1 you play as War and you get screwed over by the council that is supposed to keep the balance between heaven and hell. In part 2 you play as Death to find out what happened. The stories are parallel as @Jeykey mentioned, so you are gonna see some things from a different perspective that you already saw in the first game.