As far as I'm concerned, if you believe in Jesus and believe in God that makes some you some denomination of Christianity.
Now, just because Hitler was probably a Christian by definition does not make him an outstanding citizen, a person of sound mind/morals, or anything else our society usually attitudes to the practicing Christian.
I think this example can be placed upon a number of things. Because Hitler was a vegetarian, does that mean all vegetarians are are like Hitler? No. There is no logic to leap to in that comparison.
Extremists, fundamentalists, and the occasional crazy does not constitute an entire group of people. Christianity is not wrong because it has fire and brimstone street preachers explaining the end of the world, judgment, etc.
So, again, it is not the people that disprove a concept. It is the concept that can disprove itself, or must have someone else prove/disprove said concept. Christianity has yet to be proven or disproven to be correct, so just because Hitler fits the definition of that incredibly broud term does not constitute calling it wrong.
But, as far as who is closest to Christ...
I'm going to go with no-one.
If the Bible interpretation of Jesus is correct, then humans do not have the ability or frankly the right to compare themselves to such a deity. He is a supposedly perfect example to aspire to, but human nature seems to get in the way of that in the end.
But, if Jesus was just some normal street preacher who gained great renown then comparing yourself to such is fruitless anyway because that would imply that whoever he was has been skewed so heavily over 2,000 years that nobody really knows who he was anymore.
So, in my opinion, Hitler was a Christian. But, I warn against comparing yourself to his twisted version of Christianity in the same way I warn trying to aspire to the like of a diety. Comparing yourself to his Christian beliefs may as well be like you trying to compare your life to that of another person.
What do you gain from it? Why not accept your own beliefs and be comfortable with them instead of feeling other should be saved, or feel that your beliefs are somehow sullied by a madman? It is fruitless, and I believe the Bible warns of such comparisons as well.
But, In the end, you are human and so was Hitler and MLKjr.