Artful Dodger: There are a lot of Christian teachings that say that Jesus was a son of God, aren't there? These non-trinitarian beliefs don't view Jesus as the God himself. So this makes your argument a bit weaker. But I personally do agree that the Christian God and the Islamic God are two different entities. Wikipedia says that Islam teaches that God as referenced in the Qur'an is the only god and the same God worshipped by members of other Abrahamic religions such as Christianity and Judaism. and backs this claim by the following quote from the Qur'an (in three different translations):

“YUSUFALI: And dispute ye not with the People of the Book, except with means better (than mere disputation), unless it be with those of them who inflict wrong (and injury): but say, "We believe in the revelation which has come down to us and in that which came down to you; Our Allah and your Allah is one; and it is to Him we bow (in Islam)."
PICKTHAL: And argue not with the People of the Scripture unless it be in (a way) that is better, save with such of them as do wrong; and say: We believe in that which hath been revealed unto us and revealed unto you; our Allah and your Allah is One, and unto Him we surrender.
SHAKIR: And do not dispute with the followers of the Book except by what is best, except those of them who act unjustly, and say: We believe in that which has been revealed to us and revealed to you, and our Allah and your Allah is One, and to Him do we submit.”

However, I don't think it can be inferred from the above that the God is Allah and Allah is God.

In simple words, the two religions are too different to believe that they worship the same superpowerful being.