Infamous 2 adds little to the original Infamous, but that's ok -- the original was good enough
The storyline is pretty absent in Infamous 2, as it was in Infamous; basically, "you have powers, let's put other things with powers in front of you that you have to fight". Although, they kinda added in fighting creatures instead of other humans...so that was kinda new.
The new powers are nothing special.
This game isn't earth shattering, but the animation and play-style of both combat and exploring is really streamlined. That's what gives this game enjoyment - how they've coupled combat and movement into one seamless action.
It's probably THE BEST at combat and movement controls of any game I've played recently. That said, its worth a rent or a bargain-bin buy.