I hate to see people ignoring your thread, Mr. Pope. Sometimes it’s hard to come up with an answer to a question like yours. In my case, there are actually a number of reasons that I believe as I do, but I guess it gets down to a combination of faith and reason. As an LDS Christian, I believe that Jesus Christ did, in fact, establish His Church here on the earth as a part of His earthly ministry. I believe that He gave Peter and His other chosen Apostles the authority to oversee the affairs of that Church after His death. I believe my Church’s claim that after the deaths of the Apostles, false doctrines were introduced into the still infant Church, the doctrines Christ had taught changed over time, and the authority held by His Apostles was lost. In my studies into early (i.e. apostolic) Christianity, I have come to the conclusion that this apostasy, which was clearly predicted by Paul, actually did take place.
That would pretty much lead me to conclude that within a few hundred years after Christ’s death, the institutional Church He established no longer existed. That is not to say that there were not still a great many devout Christians around. (Mormonism is pretty liberal in acknowledging that anyone who sincerely believes himself to be a Christian, has the right to that claim.) Joseph Smith, founder of Mormonism, claimed that God had chosen him as the person through whom Jesus Christ would re-establish both the doctrines and the authority that had been lost centuries earlier. When I look at Mormon doctrines and compare them not only to what the Bible teaches, but to what some of the earliest Church fathers taught, and to what numerous early Christian sources say, I see so many, many similarities that I can’t simply dismiss them as coincidental.
To me, what Mormonism teaches about the nature of God, His relationship to us, His plan for our redemption and eternal progression makes sense. I see our teachings in the Bible and I find them to be immensely uplifting and ennobling. I also like the fact that Mormonism teaches that "the more we learn about the gospel of Jesus Christ, the more we realize that endings here in mortality are not endings at all."