I want to see the Sonic game where he's a bitter drunk reminiscing about the good old days while everyone else has moved on with their lives. Maybe Tails has a 9-5 desk job and a family, while Knuckles opened his own boxing ring. Then, like, every couple of weeks he'll come over and share a few beers with Tails, or have long conversations with Knuckles at midnight in the abandoned ring, and wonder what happened. Then, afterwards, he just... walks the streets of Manhattan aimlessly, his collar popped up against the November wind, and reflects on his life beneath the golden street lights. Afterwards he hails a taxi and goes home, ready to do the whole thing again tomorrow.
Maybe, like, the next day he's walking down the road and some kid spots him. "Hey, mommy, isn't that Sonic the Hedgehog?" Sonic smiles.
"Don't look honey, he's just a hasbeen."
Then the game just explores the life of a hero who is well past his prime, and nobody really wants him anymore. Like, he's still alive, but the worlds moved on without him. Then he looks up and sees masterchief saving the world on a giant telescreen while everyone claps. Afterwards he runs into Megaman at the local bar, and they talk for a while.