Idea's are just that. Don't know where to start? Why would that guy be trapped inside another dimension? What culture would it be (what are their beliefs)? Why do they believe he is a God? What did he do to convince them that he is a God (is he really or is he just fucking with them?). Ask yourself questions. Anybody can make ideas; It's the "Why, what, when, where, how" that make the story.
another idea i have for a story is about this guy who is traped in another dimenstion and finds a cutulutre that beleaves he is a god and even convives him that he is there god and he even gains god like powers and find that it was proficided he would appear.