A definite purchase, especially if you like Mario and Sonic or if you just like Mini-games.
There's a Single Match Mode which is pretty much like a practice mode, you can choose one event to compete in and once it's finished you can do it over or choose a new event. You can also earn Medals in this mode and set new Olympic Records and World Records. There's a Circuit Mode, which features Beginner's Class and Free Circuit, you have to unlock the rest. In Beginner's Circuit there are 4 circuits, Mercury, Venus, Jupiter and Saturn with one to unlock and each circuit features three events to compete in. You can also earn Trophies in this mode. There's a Mission Mode which lets you choose any character you want and each character has six events, four at first with two to unlock. There's a Gallery which has Olympic Trivia, Modern Olympic Games, Beijing 2008, Ancient Olympic Games and About Athletes. And there's also Records which features Records, Rankings and Collections. On Rankings it uses Wi-Fi. You can choose an event and then see a list of the Top 30 players or you can choose to see Near My Records if you're not in the Top 30, you can also Update Rankings at any time just by clicking on the Update button.
There's also a good selection of characters, 16 in all. Eight from Mario and eight from Sonic. They each have their own strengths and weaknesses. There's four different sets of characters, Power Type, All-Around, Speed Type and Skill Type and each set has four characters. Knuckles, Bowser, Vector and Wario are Power. Mario, Amy, Luigi and Blaze are All-Around. Sonic, Daisy, Shadow and Yoshi are Speed. And Peach, Tails, Waluigi and Eggman are Skill. You can also use Mii's. You can choose from six pre-selected ones as well as actual Mii's you've created.
All in all I'd have to say that this is a definite purchase especially if you like Mario and Sonic or if you just like Mini-Games. You'll get tired playing this game if you play for long periods of time but that's not a bad thing, exercise is good for everyone. It's definitly the best Mini-Game collection on Wii so far next to Mario Party 8. The events are fun and don't get too repetitive. There's definitely a lot of play time to be had especially with the Rankings being updated daily, you can always try to break new records. And if you have four friends or family members playing that's even better. There's a good selection of characters, a descent amount of events and you can use Mii's. I recommend this game to anyone, especially people who have doubts about it. Even if you just rent it you should give it a try. I give Mario and Sonic at the Olympic Games 8.5 out of 10.