To be Christian means, to me at least, to be a follower and believer in Jesus. Now please, don't get lost in the simplicity of that statement.
Jesus said a great many things, both about his relation to 'The Father', how one should conduct oneself, etc. To say that one is Christian means to believe and practice everything that Jesus said (the red text in those KJV Bibles). With that in mind, I doubt many human beings could consider themselves Christian
Which brings me to a lively joke that I'm reminded of:
[open-mindedness required]
When Jesus went back up to Heaven, God approached him immediately, rather flustered. "Jesus, how am I going to have enough room for all your Christians? Now I have to 'prepare a room' for each and every one of them!" Jesus and God, then, gathered up all the angels and spent the next few years running all around heaven, building millions of rooms for all the incoming Christians.
To this day, they're still waiting for the first Christian to enter heaven.