“Now when Jesus came into the district of Caesarea Philippi, He was asking His disciples, ‘Who do people say that the Son of Man is?’ And they said, ‘Some say John the Baptist; and others, Elijah; but still others, Jeremiah, or one of the prophets.’ He said to them, ‘But who do you say that I am?’ Simon Peter answered, ‘You are the Christ, the Son of the living God.’” Matthew 16:13-16
The fundamental reason why Christianity contends that Christ is the only way to know God is because Christ Himself claimed to be the true God (John 10:30). C.S. Lewis wrote in Miracles: A Preliminary Study:
“I am trying here to prevent anyone saying the really foolish thing that people often say about Him: ‘I’m ready to accept Jesus as a great moral teacher, but I don’t accept His claim to be God.’ That is the one thing we must not say. A man who was merely a man and said the sort of things Jesus said would not be a great moral teacher. He would either be a lunatic - on a level with the man who says he is a poached egg - or else he would be the Devil of Hell. You must make your choice. Either this man was, and is, the Son of God or else a madman or something worse. You can shut Him up as fool; you can spit at Him and kill Him as a demon; or you can fall at His feet and call Him Lord and God - but let us not come up with any patronizing nonsense about His being a great human teacher. He has not left that open to us. He did not intend to.”
Jesus said He is God and that the cross is the only way to know Him. His miraculous birth, life, and resurrection all validated His remarkable claim. There is no other path to God. Christ is the only true God.
“...no one comes to the Father but through Me.” John 14:6