If you believe Christ was the savior and that salvation comes through him and if you follow his teachings then you are a de facto Christian. If you think it is your job to judge who is and who isn't a Christian then you are doing it about as wrong as you can. You can still be a Christian of course but not a very good one.
I would say that anyone who calls themselves a Christian is a Christian.
There is no 'good' or 'bad' Christian, there is no 'right' or 'wrong' way to be a christian. Whatever someone believes is what that person believes. Nobody else gets to say what they do or do not believe.
It's not like science.