a personal appearance wouldn't do it for me. that would prove to me that he was a 3 dimensional entity and thus couldn't be "god" (at least not in the traditional sense of "god"). he'd be some sort of alien creature. if that's the case, then, like someone else said in this thread, i'd be impressed, but i wouldn't worship it.
honestly, there really is nothing that could make me "come back." there comes a point when explanations and excuses for inaction just can't cut it in my mind. the act of giving birth to a child is deserving of respect (reverence), but after a certain point, the parent has to start ACTIVELY parenting the child to continue to be worthy of respect. on the other hand, there's much that a parent can do (or not do) to stop deserving respect and "worship."