DON'T LISTEN TO THE CRITIC SCORES!!
The story is the world has been broken up into seven different pieces by the vile Dr Eggman, and Sonic and Chip must travel the world to restore it, with the chaos emeralds.
Onto the gameplay. The are two different gameplay types, Normal Sonic stages, and Werehog stages. Lets start with the Normal Sonic stages. Incredible. Breathtaking. Outstanding. How a Sonic game should be. The day time stages are so action packed, so fast and above all soo fun, you won't be able to put your controller down. There is also a level up system, so you only get faster! Along the story, there will be quite a few running stages that are side missions. This is a bit tedious. Its basicly the parts of the story levels, with certain conditions, and things to collect. And ohh the hot dog missions. Basicly, you play 2 levels 9 times each, with certain conditions. Very annoying, but only for the werehog stages. Fortuantely you will only have to do this if you want the Platinum Trophy.
The werehog stages on the other hand are not as good. Not to say there bad, but not as good as the running stages. Its basicly some occasionnly annoying platforming, and enemy combat. The levels need more variation though, and more kinds of enemies. Occasionly you will face a mini boss, but there are only two types, and they come over and over. After a few levels, there will be a boss, which are mainly easy, but are fun. You can also earn new combo attacks when you level up your combat, but you will hardly be able to use them, because combat is mainly button bashing.
Overall, Sonic Unleashed is a must buy game, especially for Sonic Fans. There is a lesson to be learnt here: what is so special about reviews? There written by normal people, and everyone has there own opinions. You never know if you'll like a game. Don't let reviews put you off a game.