So there is absolutely not one truthful tenet in any other religion but Christianity? All truth comes from God so, if any other religion besides Christianity has an article of faith, doctrine, tradition, precept, or axiom which is any way true both from the Christian perspective and from human reason, where did it come from?
I can't address what you don't ask.
Although I can say that the heaven's declare His glory and the firmament his handiwork. Also, that He has written His law in every person's heart - we all know right from wrong.
Everyone, in their soul, knows that God exists and knows right from wrong. We may deny Him intellectually or refuse to obey the moral conscience that He gave us. We might also seek to appease or to please Him apart from any revealed knowledge, thus creating a false god and a false religion.