The original Crackdown was essentially a superhero sandbox game where you had guns, too. By using your various abilities (jumping, shooting, driving, etc.), you increased your strength in that area and became stronger. Before you knew it, you were leaping buildings in a single bound, outrunning cars, and had cars that could transform into armored tanks. It was mindless fun at its best! So what did the sequel do to mess all of that up? Nothing at all.
The developers literally changed the bare minimum between the sequel and the original. A stupid story about zombies (of course) was added and that was about it. Sure, there were some minor mission additions or weapons, but on as a whole, Crackdown 2 felt exactly like the first one. In fact, it felt like cheap, rushed DLC that the developers decided qualified as a full-fledged, full-priced release. Needless to say, it was a major disappointment.