One sport that should have been good, but isn't, is fencing. You basically move your character back to dodge an opponent's attack, and then move forward to stab when he or she misses. You can parry shots, but you'd have to have lightning-quick reflexes to do so, and there's no point in doing so aside from when you have to parry to pass a mission. Another event that fails to be much fun is table tennis. The big problem here is that you have no control over your character's movement, so even if your timing is spot-on, you might be two feet away from the ball when you swing...and miss. Some of the more interesting events are the fantasy stages, where you do things such as run around a track while shooting weapons at your opponents like in Mario Kart. Another pretty fun diversion is 10,000 meter diving.
The big problem with Mario & Sonic is that the mechanics for most events just aren't much fun. The game requires some precise timing and movement to pull off certain maneuvers (you get penalized if you wave too hard when you jump), and the instructions are poor, which means that you'll spend a lot of time yelling at the TV because you just can't do the triple jump properly. Even if you aren't having trouble with an event, you probably won't have much fun--unless you enjoy waving your arms to pretend that you're running. There's also very little depth to any of the events. Other than a few sports where the controls really get in the way, it's not difficult to win gold on your first attempt. In fact, you'll probably set world records on your first go at a sport on more than one occasion. Consequently, though you might have fun for an hour or two, you'd be hard pressed to squeeze much more entertainment out of the game, even when playing with up to three other friends.
Playing for too long will have you looking like Yoshi here. Perhaps that's why the game tells you to take a break every 15 minutes or so.
The visuals are probably the best thing Mario & Sonic has to offer. You can't go wrong with the character designs, and they're nicely animated, right down to individualized celebrations. The game supports widescreen and progressive scan, so everything looks crisp and clear on a high-definition display, particularly the colors, which really stand out in HD. The frame rate is solid, even when eight characters are displayed onscreen at once--it's a very technically solid visual presentation. The audio isn't bad either. If you use the same character over and over, you'll likely grow weary of the repetitious exclamations, but there are plenty of characters available should you tire of one. The music isn't anything exciting, though you can unlock classic Mario and Sonic tunes by playing some of the trivia games, which oddly enough have you do things such as count goombas or match cards instead of actually answering trivia.
Mario & Sonic at the Olympic Games probably isn't the game you envisioned when you imagined the once-fierce rivals finally getting together, but that's not its biggest problem. Instead, the trouble lies in the often uninteresting and occasionally frustrating motion controls combined with some events that are too similar to one another, as well as shallow gameplay that brings the game down.