Looking for a game to play during my break from school (steam/PS3)

So i am looking to play a game with enough content to pass my 3 free weeks on may. I am looking a more mature game. One with a good world to explore and yet with a good action-flick as a story.

I was gonna buy vanquish at my local gamestop, but i dont really know if I should.

I am also a PC gamer, with Paradox games as my favorite ones.

Thanks,