Val, that is a BIG question! And a lot depends on what denominations you are trying to differentiate between.
I guess the "biggie" is that Roman Catholics differ from everyone else in that we are led by the Pope. The Pope is next in an unbroken line of "successors" to St. Peter, who according to Jesus Christ was "the Rock upon which the Church would be built." Catholics also believe that Mary, the Mother of Jesus was a virgin throughout her life and finally we believe that the Eucharist is truly the Body and Blood of Jesus.
Orthodox Catholics have their own leaders (and this is geographically based) but I'm pretty sure that they share the other 2 beliefs with Roman Catholics.
Episcopalians do not accept the Pope as their leader. Otherwise they are fairly similar to Roman Catholics in the basic beliefs, but not in the way things are interpreted today (they are considered much more liberal).
I do not believe that any other Protestant faith believes in the True Presence of Christ in the Eucharist, nor in the eternal virginity of Mary.
I don't have a lot of knowledge about the different Christian faiths. I hope that someone here who does, will contribute to this thread!
