Bear with me guys...
I was raised as a Catholic, went to Catholic elementary school and Catholic highschool. Answering the question, to me Mormons are Christians. To the Catholic church, that is to say, from the Pope downwards, regarding that those below the pope are in the same wavelength, Mormons and all the rest Christians religions are not in fact religions, but cults, and I agree with that. However, the word Christian can be considered by two aspects, one to refer to people, "He is a Christian", and other to refer to deeds, "That's not a Christian thing to do". Therefore, even though Mormons perform deeds which may be considered as a Christian thing to do, I cannot regard Mormonism as a religion, more over, some deeds Mormons perform ARE NOT a Christian thing to do.
The difference between Catholics and the rest of the religious christian clubs is a bit vague. Catholicism is based on The Holy Trinity, God, Jesus and Holy Spirit, however, they are the same entity, and odd as it may be, when Jesus asked His Father, our God, forgiveness for our sins, he was in fact talking to himself

. I always wondered why if Jesus was a Jew, why aren't we all Jews? Why the Old Testament is made of Jewish books? Remeber that all the main characters and heroes of the Old Testament are jews. And why did the other Jews turn on him, since it was the Son of God? Why did the sell Jesus to the Romans? And who was the Roman Emperor who some years later said "tear those fucking statues down, we are turning into Christianism", and why?
The Catholic church only considers Judaism, Islam and Buddhism religions. The rest of the Christian divisions are considered cults. They only share with catholicism God and Jesus. Some don't believe in the Holy Spirit, some do; some others don't believe in Virgin Mary and other Saints, some do. Some only believe in God, Jesus and angels. Many don't acknowledge the apostles. Some take inot account the New Testament, some only the Old Testament (the jewish part of the Bible, but they're Christians, not Jews). So, there are a lot to go round, so you can choose the one that suits you the most, so, in that trend of thought, it kinda looks like a club, not a religion.
By the way, the Catholic church doesn't regards Protestantism, Lutheranism, Anglicanism, Baptism, Presbiterianism, and all the rest of the -isms I'm forgetting as religions, they are considred cults. When Henry VIII couldn't have children he requested the Pope to grant him the chance to divorce his wife, the Pope said "WTF? No way!", so Henry started his own religion. Then Martin Luther, who was quite well off, came along and said that the path to salvation was one of faith, and faith only, no good deeds or money, things that Roman church needed.
As I said, I was raised a Catholic, and OMG, that shit is crazy. All religions are crazy. After learning how to turn the other cheek, embrace the neighbour, love the neighbour, help the poor, help those in need, and all the rest, it was shocking to see two girls of the senior year being expelled from school because they got pregnant, something clicked in my mind, something felt wrong, I mean, if Jesus was in love with prostitute and had a girl with her, out of wedlock, why this 17-year-old girls couldn't? Catholicism is some crazy shit, but Mormonism takes all the prizes... is it Kola or Kolob the asteroid were this guy lives? or is it V-612? Yes, Mormons perform some good deeds, ask an african-american person, a latino, a gay person... Racism, discrimination, very Christian things to do...
check this videos about this so called christians, they are fun, and interesting... thanks to Bill Maher
this one have some explanations about what is being discussed
http://www.youtube.com/watch?v=aKqqGX0DEMMthis is from the show on April 27
http://www.youtube.com/watch?v=Mp8jbnzrCDUthis is from the show on May 4
http://www.youtube.com/watch?v=4NLlAKKdTtYand this one is from last Friday
http://www.youtube.com/watch?v=i6L1_932Vx0
... I am not in the business of being liked anymore ...