One would think that the title of this post would be wholly unnecessary. It's more or less what 90% of the Mormon "missionaries" that have approached me over the years have acknowledged. It's clear that they deny they doctrine of the Trinity, whereas it is clear that the Trinity is accepted by all Christians.
Mormons have a new and different gospel, and a new and different prophet. They are no more Christians than Muslims are Christians.
Yet, for some reasons, perhaps for political reasons - they now wish to be called "Christians." Some misguided person has even started a blog (one post so far) called "Mormons are Christian" (link - not recommended).
Their distinctiveness from Christianity is even to be seen in the self-title that they prefer for themselves, the "Church of Jesus Christ of the the Latter-Day Saints" in contradistinction from the historical Church of our (Christians) Lord and Saviour Jesus Christ.
They refuse to accept the truth of this verse:
John 10:30 I and my Father are one.
Others, such as James White, have done much more thorough responses to Mormonism, and I'm not going to reduplicate their efforts here. Here's a link to the Alpha & Omega Ministries Articles on Mormonism, for more detailed reading. If all you've seen is "The Godmakers," your knowledge of Mormonism is probably out of date. There's a lot of material to be read. If you're interested, get started (link).