This game is so much fun and a great multiplayer. I have had it for years and still play it regularly.
The adventure mode is really neat. You can play it single player or two player, which is nice. It is difficult by yourself but lots of games are. And I got pretty far on Adventure mode by myself and I'm not an amazing gamer, so it's not as hard as people say it is. If you play it two player it is easier, but still challenging when you get farther. Most of the mini-games are pretty fun, but some get boring after a while which might be why the game isn't very popular.
The battle mode is also very fun. You can select which mini game you want to play (you can unlock extras playing adventure mode) and play with up to four players.
The best thing about this game is the variety. With the number of mini games, it's a game that will have something that everyone will like. Many multiplayers don't have that. (for example only some people like racing games) it is also farily easy to learn how to play, so it is very enjoyable to play with a group of people who have never played it before.
Overall, I think this game is really great and I am surprised so many people don't like it.