The difference is that the original BSG was, if we're being honest, a bit crap. The '03 reboot took the skeleton of a good idea (humans on the run from an implacable army of robots) and lifted it up to some of the best scifi ever made. A reboot is warranted if the original leaves space for improvement, and the more such space the better. The '03 BSG is so good that virtually no such space exists. Ditto for conversations about rebooting the Lord of the Rings; what are you going to improve on?