I play games for a number of reasons, so I can't really pick any of the options.
Sometimes I'll play to get all of the achievements (eg CoD:MW2), other times because I love the story and gameplay. Some games produce different outcomes based on my choices, so I'll replay them to see them. I enjoy a bit of multiplayer as well, whether it's FPSs or Minecraft (which is gaming crack, but in a good way).
Other times, I'll play a game once, just because I don't see any point doing the same thing again (I'm looking at you, Medal of Honour).