Mormonism

Mormonism teaches there are many gods, yet God said, "Before me there was no God formed, neither shall there be after me." Is this because God didn't know Mormonism? Or is it because Mormons don't know God?

6 I am astonished that you are so quickly deserting the one who called you by the grace of Christ and are following a different gospel - 7 not that there really is another gospel, but there are some who are disturbing you and wanting to distort the gospel of Christ. 8 But even if we (or an angel from heaven) should preach a gospel contrary to the one we preached to you, let him be condemned to hell! 9 As we have said before, and now I say again, if any one is preaching to you a gospel contrary to what you received, let him be condemned to hell!Galatians 1:6-9

Over the past 2 centuries, many people have come forth with claims of truth and prophecy: Ellen G. White (Seventh-Day Adventists), Charles Taze Russell (Jehovah's Witnesses), Mary Baker Eddy (Christian Science), and Joseph Smith (LDS). Each claimed to be a prophet of the one true church, yet they all contradict each other and Scripture. Why believe Joseph Smith over any of the others? Why believe Joseph Smith at all?

Christianity, at the present time, is no more enlightened than other systems have been. What does the Christian world know about God? Nothing; yet these very men assume the right and power to tell others what they shall and what they shall not believe in. Why, so far as the things of God are concerned, they are the veriest fools; they know neither God nor the things of God.John Taylor Journal of Discourse v13 p225

Which does the evidence support, Christianity or Mormonism?

Biblical Christianity: Mormonism:
No contradictions Plenty of contradictions
No false prophecies Plenty of false prophecies
No changes in the Biblical text Plenty of changes to the Book of Mormon