In case you missed the live Sonic Unleashed footage we covered earlier, Shadow has now been a confirmed character for Sonic Unleashed. During a live hands-on demonstration, Tails, Knuckles, and Shadow we’re all confirmed to be in the game, although no mention of how they would be implemented was discussed.
I’m a bit worried about this choice, but I’m sure Shadow fans everywhere are rejoicing. So long as he doesn’t have guns in this installment… and doesn’t act all *gangsta* or any of that crap, I’d say there’s still a chance he’ll make a good addition to the game.

yes, i completed the game for the Wii and PS2 (they are the same version) and i think Knuckles and Shadow will appear ONLY in the Xbox360 and PS3 version (they are a Director’s Cut versions from the Wii/PS2 versions, but with more levels)
sorry for my bad english, i’m from spain.
I beat the game twice and still no shadow
to all you guys you all are right shadow isn’t on sonic unleashed because i beat the whole game and i did not see him in any levels