http://gamerlimit.com/2011/06/e3-top-pick-dead-island/
Quests are one of the pillars of Dead Island and they do well to set it apart. Most other zombie games focus on escape, which often translates to reaching a singular goal. They may try to ratchet up the tension with a time limit and sudden shocks, but once you get from point A to B, there isn't much left to warrant a replay. Dead Island disrupts this model by making you beholden to your morals, and your character responsible for the living.