Dear Drought,
Interesting you should ask.
I just posted under "Was Jesus God," namely Posts #10 & #12, some things you may find applicable to your question.
I'm wondering why you would ask this, or want a "list." [Rhetorical thought, though.]
Some denominations are considered not genuinely Christian because:
1) They man not believe in the Trinity of God. (See my remarks under "was Jesus God?")
I believe both Jehovah's Witnesses, Mormon's (Church of Latter Day Saints), and what's generically termed "Oneness" churches are this way. I also believe the first two I mentioned do not believe in salvation by Grace alone - through faith in the finished work of Christ upon the cross. This would disqualify them from true Christianity. But some members may still have found the truth and personally experienced genuine salvation. There's no way for any of us to know, unless the Lord specifically and supernaturally reveals it to us for some personal reason (such as if we need to know if the person we intend to marry or go into business with, is truly a believer - but this must be kept confidential between us and God).
I personally do not know which, if any, Oneness churches believe in salvation by Grace alone. (Btw, any belief other than Grace is a disqualifier because it is self-righteousness: someone erroneously believing there's anything whatsoever possible which is considered good enough for an unholy human being to have a relationship with a holy God.)
2) We cannot determine someone's salvation or lack of same by asking them questions and judging their responses. Someone's knowledge of doctrine does not limit God and His Spirit. While we can possibly deduct for certain that some are NOT born-again if they preach an outlandishly opposing doctrine to that of Grace by faith alone, again, only God knows who is and who is not His.
3) Some denominations are judged false because they have added books - as someone else said - and/or extra-biblical revelations which they believe are necessary in order for man to know to be saved, and/or they alone have supposedly ordained-by-God people needed as intermediaries. There is no proof to substantiate these superstitions in scripture, and in fact much to prove they are false Christians.
4) There are also what is called "Mainline," or liberal, denominations. These often started decades or hundreds of years ago as genuine Christian groups, but after the first generation of believers, these were increasingly found to be attended by those who didn't have themselves a born-again experience, but who practice Christianity by the LETTER of the law, and not by the Spirit of it.
In other words, anyone can take the Bible, extract and implement its principles and ordinances to a great extent, and call themselves "Christian." But those who are considered by God to be His true children, have had an instantaneous and supernatural experience, known as the New Birth or being born-again, when they were changed in the spirit realm from something unclean to a child of the Heavenly Father.
We as Christians are warned not to unjustly discern the body of Christ. While some could interpret this to mean we are called to walk in unconditional Love with all and especially the brethren - and this is true, others see in this scripture a warning not to judge someone as not being a true believer because they either don't believe all the pet doctrines we do, or they don't act saved, or they didn't understand what really happened in the Spirit realm when they were saved, etc. The penalty for those of us who so judge is an early death.
I made some add'l. comments on the charismamag.com forum - click on Letters to the Editor, click on "Was Jesus God" topic - that further expound on what I stated here.
But unless you're wanting to get married or otherwise join in some type of partnership with someone, there's no need to worry about any of this. We are commanded to rather make sure our own salvation is sure. If we come accross those who God knows are not saved and who He wants us to witness to, we can trust Him to make that known as He wills and if we're walking in the Spirit and can therefor hear Him.
---P/N/B/
