I was looking at a bunch of Usenet posts back at the time of the Sega CD launch, and one thing I noticed is that a bunch of people seem to talk about Sonic 2 having a CD version on the Sega CD. It seems that somewhere along the line, Sega was just thinking of throwing Sonic 2 on a disk, adding some great CD music and a few cinemas, and then calling it a day. Maybe they were going to add a few extra levels to the game or whatever.
Instead, Sega decided to make a completely separate game than ended up being the Sonic CD game that was released.
I wonder if there is a proto somewhere out there with the iso of Sonic 2 on a CD with CD music. How awesome would that be ? I mean, I like the Sonic CD game quite a bit, but I think Sonic 2 is a better game overall, and it would be awesome to play it with some sweet CD quality tunes.