I'd...probably take a moment to gawk and laugh. (Because, mainly, no one knows what God looks like, so how can I know that the person standing before me really is him?) After that, I'd ask him about stuff that science currently can't answer. How did the world start? Is there even such a thing as world peace? And that continue with my own personal questions about the bible (eg why is there suffering) It'll be amusing, if that does happen.