As a matter of fact, I met some fishermen in Greece who pray and even leave offerings at a Poseidon shrine. I am not quite sure how much they actually believe, nor do I know how much my neighbors, who go to Church on Sunday, believe in Jesus's divinity.
But I do know that either one billion of Christians are right and one billion of Muslims are wrong about Jesus's divinity, or vice versa. So, even if I were, for some reason, to accept one holy book before all others, I would still know that significantly more than two thirds of religious people are dead wrong, either because they reject the Savior, or the Prophet, or whomever.
And lets not forget that many Christian denominations' doctrines say that most Christians are dead wrong, or at least wrong enough not to have a shot at Heaven. The same applies across many divides inside other religions. I have not done the footwork myself, but I have read solid arguments that no matter who is right, more than 90% of religious people are wrong.
Now, I do not claim to know the Truth. I believe in small truths, like, for example, that it is impossible to disprove the existence of an all-powerful, all-knowing entity. And I know better than to waste time on debating matters that cannot be disproved. But those are facts:facts:
1. More than ninety percent of all people on Earth are wrong in their religious beliefs.
2. The best predictor for people's religious beliefs is what they have been exposed to in their formative years.
3. Most holy texts assign heavy consequences to not having the right religious beliefs, and living according to them.
In light of the above, I have, personally, decided that I cannot respect, let alone worship a deity that's OK with the situation. So, at the end of the day, I make no difference between people who believe in Poseidon, and people who believe in the deity in the Bible/Torah/Qur'an. At at the end of my life, I may be in for a surprise. But I think I'm about as likely to be collected by the Chosers of the Slain as by a devil with a pitchfork.