Excellent game with a lot of space to cover on foot or in a vehicle. Climbing and jumping buildings is a blast.
The difference is that in Crackdown you get to go up as well. Not in a helicopter, but on foot. You can climb just about any building and are rewarded most of the time for doing it. That's where the fun part comes in.
You create your own character based on your actions. You shoot a lot of people with a gun, you rake in the XP for shooting. When you neglect using explosives, you stay weak in that area. The gathering of XP is highly visual and gives the process an extra impulse.
As I said, scaling the buildings is rewarding in that it rewards you with XP for agility. Making you stronger. It is highly addictive to collect all of the XP available.
Combine this with a sprawling city with lots of civilians and bosses to kill and you have a great game that grows on you when time passes.
Negatives to the game are the driving of the vehicles, which is generally pointless, and the difficulty level. Although you can change the difficulty when you finish the game, this does not negate the feeling that there is a point in the game where your character becomes too strong and the skirmishes with the gangs become repetitive.
Let's hope Crackdown 2 addresses these problems and leaves all the good bits where they are. Then you have a cracking game.