Perhaps it’s a combination of format, flexibility and creative teams. Certainly, movies lack the space to do a great deal with a concept. TV shows provide more breathing room and comics even more so, given that your ‘budget’ is effectively unlimited. That said, comics are no guarantee either. Firefly should have been an obvious comics hit: fill in the gaps from the end of S01 to Serenity and then forge ahead. But almost every comic I’ve read in that universe has been utter shit.