Hi Liberate, Joseph, thank you for your comments.
In short, one can know God by innate capabilities. God put that in our hearts. Put a small child on an island alone. He will grow and start to think and ask questions. He can think of a mighty Creator (whose attributes are more or less like One God in Islam.) As for trinity, that has no hope. That cannot be known unless someone tells him God is such and such. So Christianity depends on the person and testimony of Jesus, not God. And thats where the strong appeal of Islam lies. It does not call people to believe in something which does not really echoe in their hearts and minds.
Joseph, I wont discuss specifics of Islam and Qur'an here, since thats not the core issue. Also I dont feel compelled to read any links provided here. Discussion goes on here, not somewehere else. And please take it easy.
Regards,
Unite