Superman said,“Christians generally classify any religion other than theirs as false. Who or what gives them the authority to do so? Would it be fair if Buddhists, Atheists, Muslims, Hinduists call Christianity a false religion?”
Athiests declare there is no God. They make an absolute statement. They most atheists think people of faith are weak and that anyone with a faith in god are wrong.
Muslims deny Christianity and claim that all those who deny Allah perish.
We do however like you said think other religions are false, you are right about that.
We believe that all roads do not go to heaven.
Jesus says in the Bible, “ I am the Way, the Truth and the Life….no one comes to the Father but through Me"
Notice He doesnt say "a" way, He says "the" way.
That eliminates everyone else,,,,,allah, buddah, etc.
He also says, ""I tell you the truth, unless a man is born again, he cannot see the Kingdom of God... unless a man is born of water and of the Spirit, he cannot enter the Kingdom of God (John 3:3,5)."
He also says,
"I am the Door [Gate]... by Me if any man enter in, he shall be saved (John 10:9a)."
"'So how can we know the way?' Jesus answered, 'I am the Way [Path]'... (John 14:5,6ff)."
Jesus CLEARLY said, I AM THE WAY.