I finally found some new info on sonic unleashed(not that I was trying to hard anyways I just pretty much went to one website^^')
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characters
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Sonic / Super Sonic / Werehog-Sonic
Eggman
Tails
Knuckles
Amy
Sonic is the only playable character in the story.Tails ,Knuckles ,and Amy are playable only in minigames.

All of the levels in the game will be based on real-world locations. The first level of the game, Mykonos, was initially dubbed "Greece", due to its design being based on the country, and will be used to initiate the player into some of the game mechanics, as well as provide a sense of speed. The fourth level is based on Europe. A further level seen in screenshots shows a sandy, desert-like level, and two more levels have been shown to journalists, which comprise a level in China - including a run along the Great Wall - and a level based on New York, where Sonic was shown to run betweens skyscrapers.

Levels will have multiple pathways for players to follow, and a day and night system for levels will be introduced, whereby different levels will take place at a set time of day. However, the system will not be dynamic for each level, meaning that time will not advance during the action stages.

The game will also feature Town Stages, and players will be able to walk around the environment freely and speak to townspeople; however, this "overworld" can be completely ignored, should the player prefer to simply play through all the stages. Side quests will also be available from the Town Stages, whilst players will be able to gain various extra items by talking to different townspeople.

-info found here

and sorry it's only 1 player but that might change

and yet another pic of it: