Recommended: Saints Row 2

As the helicopter flies into the sunset: "What do we do now?" "We own this city. We can do whatever we want." Cue the end credits for Saints Row 2!

Yes, I finished the game and had a blast. As I've said, I'm a lousy video game player so my experience may not be typical, but on "casual" I found it challenging without ever being impossible. (I found it harder than Skyrim, but there I stumbled upon an optimal combat strategy so my Skyrim experience may not be typical.) There was a lot to do, from fighting to chases to "ho-ing" to driving around on fire in an asbestos suit, with a wacky humor that made me LOL quite a few times.

If you don't mind playing a violent sociopath -- and I wouldn't hold it against you if you do! -- I would highly recommend Saints Row 2. Only $15 on Steam, and it runs smooth as silk (only crashing once in 60 hours of gameplay, nearly unheard of for PC games on my machine). Check it out, yo!