It's safe to say that the far majority of the people on the planet know about the concept of hell. (Certainly all Christians, Jews, and Muslims do; many Hindus, Buddhists, and atheists have had enough cultural cosmopolitan exposure to have heard something about it.)
My referring to the fire was, of course, just an analogy, not about the certainty of the fire (which is the direction you are taking my analogy), but about a person's choice for salvation or fiery consequences. As we have discussed, the evidences for the existence of God outweigh the evidences against his existence, but that fact persuades few who still claim "There just isn't enough evidence to sway me towards theism." I think the question still is: What evidence are you looking for that would accomplish that?" My honest wondering is that there is no such evidence. Most people, I think, are saying that because they are choosing not to believe, not because they've objectively analyzed the cases pro and con.