Are Mormons Christians?

This Sunday, I attended a Methodist worship service as well as part of my traditional Mormon "Sacrament Meeting." My son and daughter play in the bell ringing choir at the Methodist church, recruited by my son's girlfriend. My husband, other children, and I have now attended multiple services there, as well as evening fundraising dinners at this local church. This has led me to think more carefully about why it is that many Christians do not consider Mormons to be part of their group, and why Mormons are so vociferous in our demands to be included.