The strongest historical fact in all of Christianity is the death of Jesus of Nazareth on a cross by Roman crucifixion. Muslims say that this did not happen. Muslims choose to differ with Christians over our most grounded fact in history.
Many Jews were put to death by Roman crucifixion. This is neither "special" in itself nor unique. What IS unique both historically and religiously is that
He rose again, leaving an empty tomb. No one can defeat death by delaying it ... even for thousands of years. Jesus defeated death by entering it and breaking out, demonstrating that death
could not hold him, even when he submitted to it. This is the fundamental historical fact underlying the Christian faith. And Paul himself said ...
1 Corinthians 15:13-19
If there is no resurrection of the dead, then not even Christ has been raised. And if Christ has not been raised, our preaching is useless and so is your faith. More than that, we are then found to be false witnesses about God, for we have testified about God that he raised Christ from the dead. But he did not raise him if in fact the dead are not raised. For if the dead are not raised, then Christ has not been raised either. And if Christ has not been raised, your faith is futile; you are still in your sins. Then those also who have fallen asleep in Christ are lost. If only for this life we have hope in Christ, we are of all people most to be pitied.
Without Christ's resurrection and all it implies (the sinlessness and obedience of Christ, thereby His (highest) standing with God, His authority over everything given Him by the Father, His role as our intercessor, our reconciliation, our recompense, our hope, our goal, and much much more) faith in Christ is not only useless, it is downright pitiful self-delusion! It is even blasphemous in falsely representing God. But it is the resurrection that gives Jesus' death on the cross its supreme value - in the resurrection Jesus' righteousness is vindicated, his death is given value as a means of redemption for all those who believe in him.
Other significant differences between Christ's teachings and those of Mohammed (and to some degree even Judaism) include "love your enemies, bless those who curse you...," justification by faith graciously given by God, that none of us can come to faith "unless the Father draws us" (we are unable even to seek Him on our own, let alone please Him with our good deeds and offerings), a model prayer that includes the "downward" movement of the kingdom of God from heaven to earth NOW, within the hearts and lives of believers. The core "social morality" (as depicted in the 10 commandments) is broadly similar in all the major religions, including Islam, but it is in Christianity that we find that simply holding to these commands we do not and cannot earn our salvation (for instance they do not even address sins of omission - not doing bad things is NOT the same as doing good things). And there's much more.