It doesnt need much content because of the way it works.
The game has real replay value up the wazoo. By which I mean that rather than having to play a game through twice exactly the same way to see some different cutscenes you can actually play the game several totally different ways and have completely different experiences.
Anyway I <3 crackdown, I'm rarely sucked into the whole sandbox thing, but just jumping around the beautifully crafted city is worth the price of admission alone here imo.