Seems I went back to Sonic 1 to try get my last achievement, noticed that the game needs to be unlocked or repurchased or w/e
So I went to look at the purchase thing which thankfully still showed that I had already bought it, seemed fine.
Here's where it becomes confusing, I redownload the 'bought' version according to my game, go onto 'play' as soon as it's sort of instant finished.
But that doesn't fix the problem. It's becoming a pain since its nearly 3am here, can't really phone at this time.
Anyway tried deleting the file, even redownloaded it from the download history/marketplace/in-game but no luck.
Also I now its not to do with license porting since I tested Doom from my old Xbox, I know for a fact Sonic 1 has worked on my newer Xbox S, had the new S since the release.