100% completion, and it was worth it!
The whole fun of this game stems from the randomness of the mini games. As stated probably in countless reviews, the first play thorough the game is easily the best, because you have no idea what's going to come at you. After you have played all the games it is still fun, it just does not make you crack a smile when you see a new mini game.
I actually had played this game to the end of the story mode, then dropped it for a couple months, then came back and just went on and got 100%. It was actually more of a grind match to get 100% and the end result was really not worth it because the games lose there fun, but at least I have bragging rights.
Even with that though you should still pick this game up because I promise you will not get tired with this game for at least 20 hours, and in todays world that is some good value.