I received this game as a birthday gift from a friend, and I was not quite sure how it would play out.
This is a game that I would have peed myself over when I was younger. Sonic is (obviously) one of the playable characters, which alone would have appealed to me. There are a lot of Sega characters to play as, most which have to be unlocked through gameplay.
Sega Superstars Tennis is the equivalent to Mario Tennis, with better graphics and challenges. Since I loved Mario Tennis when I was younger, I found myself entertained by the Sega version. There are fun challenges to play, such as hitting zombies with tennis balls, clearing Puyo Pop walls, and avoiding police while running around the court. Normal tennis matches are available to play, either in single player or multi-player. These are not boring, since Superstar mode is an option, which gives you a special move to hit the tennis ball with special effects going with it. For example, Dr. Eggman throws bombs with his tennis ball, which causes the other players to freeze for a few seconds, allowing you to hit the ball past them.
The computer players difficulty levels differ on every round. Sometimes they will be impossible to get the ball past, and other times they will stand by and watch the ball fly past them. As with the computer partners, they will either help immensely or not hit the ball and wait for you to hit it. Their tactics are not something to get frustrated at though, since it's not repetitive enough.
Each court is themed by one of Sega's games and comes complete with it's own set of music. Different music tracks from the games can be unlocked as with the characters.
In the end, the game is fun and doesn't have too many flaws. It is a treat for Sega lovers and Mario Tennis fans.