Christians & Muslims do not pray to the same God. The God of christianity is made up of the Father, Son & Holy Spirit whereas muslims deny that God is the head of the holy Trinity.
As to your statement that prayers go unanswered, well that depends on what your praying for & your motivation for asking.
God always answers prayers, His answers are Yes, No or Not Now. The biggest hurdle is to LISTEN for the answer, because our answers are not neccessarily Gods answers.
