Would Jesus really be a Christian if he were to come back?

he would probably be an Atheist Buddhist.

A Christian by definition is a follower of Christ. So Christ could not become a follower of Himself; but then again He was in a sense, being the first to behave according to His own teachings.

There is an interesting point that you raise in your question. The teachings of Christ are not followed as they should. But this is a natural process. Everything in life has a birth, a time of maturity, and an old age. Spring is followed by summer and autumn and finally by winter. But then, there comes again a "new spring". This "new spring" brings the same effect as the previous spring and the only difference is the name. One was the spring of "2006" and the other, the spring of "2007".

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21 “Not everyone who says to Me, ‘Lord, Lord,’ shall enter the kingdom of heaven, but he who does the will of My Father in heaven.

there are people who call themselves christians but arent. most of the time, because they are misled by false prophets. Read Matthew 7:15-20

Jesus was born a Jew, lived a Jew, died a Jew and was buried a Jew. IF he came back, why would you think he would come back as anything other than a Jew?

(Course, he was not a very observant Jew so my hypothesis could be wrong.)

He might be a christian but I think he would shun organized religion.

Yes, I think he would be.

And, by the way, what have you done today to help out your fellow human beings?

he was born a Jew but Christianity is the fulfilment of the jewish scriptures

yes he would....