We just learned that the original Sonic The Hedgehog is an unlockable bonus in Sonic Generations. Just in case that wasn't enough classic Sonic for you, if you pre-purchase Generations from Steam, you also get Sonic 3D Blast and Sonic 3 and Knuckles.

Click here to pre-purchase now, and begin playing your freebies right away. You will have to wait until November 1 for Sonic Generations, though.