PtoPOnline has the most detailed look of B.C. ever shown. Made by Lionhead Studio's satellite Intrepid, and eventually cancelled in 2004, this game is one of my personal holy grails for all unreleased games, let alone Xbox titles.
Thanks to IGN for preserving the old video from Intrepid, and to all game press outlets that keep their old articles online. And of course my pals over at Unseen64!
It is believed that this video falls under fair use for educational and research purposes. All games, whether cancelled or released, deserve to be documented and preserved for future generations.