I kid you not, the guy behind the petition was upset Ghostbusters was getting a sequel and Back to the Future wasn’t.
The difference being Ghostbusters and its sequel had an ending that was still open, which is what led to the cartoons. Back To The Future was a definite trilogy with an ending. Robert Zemeckis has stated the movies are done and will remain done. You’ll have to settle for alternate unofficial media.
BW Media Spotlight 
