In an ideal world, there would be no intellectual property ownership, no hiding away of concepts for private gain, and ideas would flow freely between developers like tides of fairy dust. Everybody would have the right to leverage any fiction or approach, quality and quality alone would determine the definitive interpretation, and we'd all live happily ever after, eating jam and pies.
Heck, this could actually be the way things work. Perhaps all those copyright spats are just melodramas they've cooked up to keep us interested between screenshot mail-outs. You never know. Just in case, here's a list of franchises that might perform better in another studio's hands. Feel free to take heed, publishers.