G-d has a different nature and character in the Jewish faith then Christianity and Islam. I do agree with Muslims that G-d or Allah in Arabic have the same nature. In the Christian faith the Trinity is very popular and that divides G-d.
Judaism insists on a notion of monotheism, the idea that there is One God. As Judaism understands this idea, God cannot be made up of parts, even if those parts are mysteriously united. The Christian notion of the Trinity is that God is made up of God the Father, God the Son, and God the Holy Spirit. Such a view, even if called monotheistic because the three parts are, by divine mystery, only one God, is incompatible with the Jewish view that such a division is possible. The Jewish idea is that God is one. This idea allows for God's unity and uniqueness as a creative force. Thus, for Jews, God is the creator of all that we like and all that we don't. There is no evil force with an ability to create equal to God's. Judaism sees Christianity's trinitarianism as a weakening of the idea of God's oneness. Jews don't have a set group of beliefs about the nature of God; therefore, there is considerable, and approved, debate within Judaism about God. However, all mainstream Jewish groups reject the idea of God having three parts. Indeed, many Jews see an attempt to divide God as a partial throwback, or compromise with, the pagan conception of many gods.