There are dozenz of Evangeligal groups, ministries, and churches. All consider each other Christian for one basic reason. They are the ones that do not believe in a single truth. To them there is a truth for each church. They give a list of seven or eight core beliefs, but anything else is up to each individual group. I have heard it said that the great thing about Christianity is that the a belief in the Bible and Jesus allows for these verying beliefs.
On the other side, it is generally held that any church who holds to the doctrine of absolute truth, and that they have it, is not christian. The reason is that this does not allow the differences that Evangelicals allow. If these differences were not allowed they would have to question which church really had teh truth, which most people find to difficult to research.
Me personally, I am LDS and have asked several times for people to use the name of my church correctly and with respect. I have also posted on the deffinition of the term Christian. It was first used in Antioch by the saints wishing to distinguish themselves from the surrounding pagans. It is, therefore, simply a term that means "a Follower of Christ." I enjoyed C. S. Lewis's book Mere Christianity where he devoted an entire chapter to this topic.
Also, I would not suggest substituting the term Chatholic with the term Christian, just as I will never substitute the term Latter-Day Saint with Christian. We are all christians, but I am of a particular denomination that I believe to be the true church of Christ. When we start substituting our church's name for the general category of Christian, we show an acceptance of the view that our church is not Christian, so we must change. I am unwilling to do this, and would not advise anyone else to do it either.