I am not sure about south park, but I did play Infamous & Infamous2. I actually liked both the games but I do agree, the second gets a little monotonous after a while.
Having said that, second son is one of few games that got me really excited about PS4. Actually that's the only game that got me excited for PS4, even though I was excited enough to pre-order WatchDogs (for PS3).
So, I'd love to get the second son; though, I am not one to complain about winning free stuff.