Middle-Earth: Shadow of Mordor is going to change everything.
Iteration can be a slow process in video games, but every year or two we get a jump-start with an idea so revolutionary and perfectly-executed that it creates a roadmap for others to follow. Shadow of Mordor's "Nemesis System" is the heart and soul of this latest journey to Middle-Earth, creating a constantly shifting hierarchy of foes to battle. Navigating the messy world of Uruk politics allows you to create your own player stories in a way that is more engaging and personal than the usual scripted events. The eventual ability to assert your own influence cast a further wrinkle into an already groundbreaking idea.
Still, Mordor may not have made the cut in our year's favorites if it weren't so refined from top to bottom. It borrows parts from both the Batman: Arkham and Assassin's Creed series, and matches or exceeds them both. Every mechanic from the rhythmic combat to the stealth simply sings. It also, strikingly, sets itself in the familiar tropes of the Lord of the Rings series, but finds a way to tell an original story that feels like it has some weight and impact to the events with which we are already familiar.
Middle-Earth: Shadow of Mordor began its life chastized as an imitator. Its combat and stealth influences made it appear to be a competent licensed game, but little more. Much to our surprise, it turned out to be more original than met the eye, and no one can fairly call it an imitator anymore. If anything, other games will be looking to imitate it.