At first Mario Tennis is great !! But after u have unlocked DK JNR and Shy Guy and then played all the ring stages all that is left to do is complete the game with EVERYONE to enable them to use the star option.
(When selecting hold R)Then multiplayer is all to keep you going.
Mario Tennis an excellent game and I have it. My whole family loves this game and it has excellent modes, games and characters. The best player according to me is Luigi because he is powerful and is quite fast.