6. Crackdown 2
In 2016, who even remembers Crackdown 2? Although the original is fondly remembered by early Xbox 360 players (and the upcoming third title is certainly reigniting interest in the series), the first attempt at a follow-up was more of an expansion pack than a fully-fledged sequel. Taking place in the exact same city - although this time overrun by zombies (because that had never been done before, right?) - the second game lost much of the personality and character that made the original so fresh and unique. Helmed by a new studio and pushed out the door with little fanfare, Crackdown 2 felt like a stop-gap release onto a bigger, better game that never came.