Michael Otterson, director of media relations for the LDS Church, has a lengthy and thoughtful discussion on this issue over at the Washington Post. Key paragraphs:
When someone says Mormons aren’t Christian – and I’m trying not to break Stendahl’s first rule here by interpreting conservative Christian thought incorrectly – he or she usually means that Mormons don’t embrace the traditional interpretation of the Bible that includes the Trinity. “Our Jesus” is somehow different from “their Jesus.” Further, they mean that some Mormon teachings are so far outside Christian orthodoxy of past centuries that they constitute almost a new religion.
The irony is that most Latter-day Saints wouldn’t argue with those statements. When a Mormon says he or she is Christian, they are not trying to minimize differences or fudge the issues. Mormons are well aware of the many deep doctrinal differences with other Christians. For instance, Mormons reject the Trinity as non-biblical, and believe the concept to be the product of the creeds that emerged from the 4th and 5th centuries. Further, while embracing the Bible (the King James version is preferred), they don’t interpret it the same way as some Protestants – for instance, that the earth was literally created in six days of 24 hours. Neither do they believe that the scriptural canon was closed with a period and an exclamation mark after the death of the apostles, but that God is perfectly able to talk to prophets today as He did in ancient times.
But for Mormons, these belief differences have nothing to do with whether or not they are Christian in the true meaning of the word. Mormons believe in the Jesus of the Bible, the same that was born at Bethlehem, grew up in Nazareth, preached His gospel in Galilee and Judea, healed the sick, raised the dead, and finally offered Himself as a sinless ransom for the sins of the world. They believe that Jesus Christ was literally resurrected, that He lives today, and that He is the only name under heaven by which mankind can be saved. This is the Jesus whose name is depicted on the front of every Mormon place of worship. This is the Jesus in whose name every Mormon prays and every sermon is preached. This is the Jesus whose body and blood are commemorated in weekly worship services by Latter-day Saints from Nigeria to New Zealand, from Michigan to Mongolia. For Latter-day Saints who try to live their lives as they believe Jesus taught, assertions that they aren’t Christian are as bewildering as they are wounding.
Mormons have no argument with assertions that they are not “creedal Christians,” or not “orthodox” Christians or “Trinitarian Christians.” Frankly, the whole point of Mormonism is that it is different. Just how different is best explained not by pastors of other faiths, or by secular journalists or by those whose self-interest lies in marginalizing a growing religion, but by Mormons themselves.
P.S. And if you missed it, note the rejection of strict creationism in the 2nd paragraph quoted above.