Aren't’ there also similarities between Mormonisn, Catholicism and Islam as well? Seems I've been coming across those similarities now that Islam is being better known and understood. I also have seen “Chrislam” as the churches appear to be merging their services from time to time....dangerous ground the church is on these days.
Note however that the EOs dissent from claims of papal power and jurisdiction, (http://www.ocf.org/OrthodoxPage/reading/ortho_cath.html) though they do hold Tradition as basically the same as Scripture and their faith as being the one true faith, and disagree with Rome about what Tradition teaches (thus the split on the Filioque, and rejection of Rome's purgatory, etc.) but are less precise in defining doctrine. And which goes back a long way. (http://www.stpaulsirvine.org/html/TheGreatSchism.htm)
Of course, there are commonalities among all religions, but in the "Christian" realm, besides other doctrines, i see the key distinctives as being a supreme (over that of Scripture) assuredly infallible-type authority, and another source of Divine revelation on faith and morals which is made as equal in authority to Scripture, and out of which traditions of men are taught as dogma from God.
These are also marks of groups such as the Watchtower Bible and Tract Society (so-called "Jehovah's Witnesses), but which require lock-step agreement with their leadership and writings beyond even a few core truths but even extending into prophecy. (http://peacebyjesus.witnesstoday.org/TheBIBLEandSoCalledJEHOVAHS-WITNESSES.html)
Evangelical-type Protestants are sometimes attacked as if we followed Luther as if he were a pope whose writings were infallible, but which is manifestly not the case (i think Sarah Palin commands more loyalty!) though without one centralized authority (which typically exists on a denominational level) evangelicals do overall hold to certain common core truths as a result of subjecting truth claims to the test of Scripture as supreme, while varying degrees of interpretation exists in issue outside of these. Catholics have their own centralized authority (which effectively is restricted to their church) and are required to give assent of faith to its few infallibly defined teachings, providing they understand which ones are, in which there some interpretation is required as concerning the breadth of them and some of its meaning, while it is understood that some dissent is allowed in the majority of teachings, and great liberty exists in interpreting Scripture to support Rome. But uncritically following men also exists among those who claim to be born again. (http://peacebyjesus.witnesstoday.org/Hinn-trueorfalse.html)
As in Scripture, truth is made manifest by its qualities, effects, conflation and supernatural attestation, with the gospel of grace today effecting manifest heart and life-changing regeneration, and not by the formulaic assertions of men.