You want a very quick way of distinguishing Islam from Christianity? Think of the cross. The Muslim account of the cross exactly reverses the gracious work of Christ.
In Islam, the sinful man (Judas) is substituted for the righteous one (Jesus). The Quran says it only appeared to be Jesus on the cross, another was substituted in His place. The Hadith (Muslim writings that interpret the Quran) claim that the one substituted was Judas. All this happened because justice demands the death of the bad man, not the good one. It was necessary for the unjust to be punished and the just to escape. This is the judgement of human religion.
Yet the truth is the exact opposite of this very human sentiment. Instead, the righteous One (JESUS) was substituted for sinful man. He swapped in for the guilty and died in their place. He determined to be the Just One punished so that the unjust may escape.
He who knew no sin became sin for us so that in Him we might become the righteousness of God. (2 Cor 5:21)