Sonic: The Neo Realms

Sonic: The Neo Realms is a Sonic-series fan game created by JudgmentTH with the RPG Maker 2003 engine. So far, no story hasn't been shown yet, but a demo is expected to be released during summer/fall 2010.

Story
So far, the only story is that Knuckles is knocked down by Dr. Ivo "Eggman" Robotnik, and Sonic enters in time before Eggman can steal the Master Emerald.