I spent most of the game playing 2 player with my brother (which was amazing). A few days I had some friends over and got to try out 4player and it was, without a doubt, some of the most fun I have ever had in a video game. Not only were the 4 players having fun, but people who were just watching were having a blast! I even got my dad, who NEVER plays games, to play with us without even asking. He thought it looked fun and wanted to try it out himself.
Every sale NSMBWii gets is 100% deserved.