Films that could have been, but ultimately were cancelled ..

I wasn't exactly cancelled but I kind wished Tarantino went ahead and made The Vegas Brothers with John Travolta and Michael Madsen.

Paul Verhoeven movie about the Crusades starring Arnold Schwarzenegger, Jennifer Connelly, Gary Sinise and Charlton Heston.  

Neil Blomkamp Alien movie

And while Vin Diesel still said he has every intention of making it, his movie about Hannibal Barca.