Well because the only real encounters i've had with God are when i've prayed to him as or in the name of Jesus. Also bits in the Qur'an similar to the bible, the fact that the bible was about 500 years old when the Qur'an was aparently revealed to Mohammed, seems suspicious. I know in my heart that in Jesus i can rest assured i will not see eternal torment. When i pray to God, when i read the bible and really understand, i feel a great sense of peace and love that could only come from God.