Messiah means....a leader regarded as the saviour of a particular country, group, or cause. Jesus, peace and blessings be upon him and his family, was given this title, and will attain this title more so when he returns, in his second coming. This will be when he tells the Christians the truth as to what they were previously believing in....in a false assumptions.
Messiah does not mean he has to die on a cross....who made up this assumption, ask them? this is nothing but conjecture and mindless hope and confusion on their part. Christians have no real recourse as to how to explain there own beliefs.
And because of their disbelief and of their speaking against Mary a tremendous calumny; And because of their saying: We slew the Messiah, Jesus son of Mary, Allah's messenger - they slew him not nor crucified him, but it appeared so unto them; and lo! those who disagree concerning it are in doubt thereof; they have no knowledge thereof save pursuit of a conjecture; they slew him not for certain. But Allah took him up unto Himself. Allah was ever Mighty, Wise. There is not one of the People of the Scripture but will believe in him before his death, and on the Day of Resurrection he will be a witness against them - 4;156-159