No... You can believe in the Devil and worship him without believing that Jesus Christ is the savior. Believing that Jesus Christ is the savior, that there is one God, and living for Him instead of anyone else would be what it means to be Christian.
And then Jewish people just follow God and believe in the Torah which basically says Jesus, having been a human, could not have been the savior, or the Islamic, who think Muhammed was the best... Yeah. Point is believing in SATAN could never make you Christian.