Are all Christians going to enter hell fire?
A Muslim is not entitled to decide on whoever will enter Hellfire and who will not; rather, a Muslim is required to teach people the sound concepts of the religion and be merciful towards them.
The rulings of this world differ from those of the Hereafter. However, a person may be judged in this world as ostensibly being a disbeliever because he did not enter Islam, when in fact he did not doubt Islam in the first place. This judgment does not necessitate that such a person be from among the people of Hellfire nor that it be his eternal abode.
Such a person may be excused before His Lord the Almighty because the message of Islam did not reach him in a clear manner or because the call did not reach him at all. Therefore, he will be among those whom Allah will test on the Day of Judgment.