It's just as simple as ABC, but only for those who knows.For the ignorant (eventhough call themselves muslims)and the kafir (non muslims),to admit that Allah is the name of god for all religions, is  ridiculous!Firstly one should know the meaning of Islam (surrender).It is for us muslims to surrender ourselves in all our doings, all the good deeds, to our only god ~ Allah. Islam is to surrender, submit oneself inwardly and    wholly to the one god which is most merciful and most gracious.Surrender to Allah's love, in the hope of becoming his lover,to feel his love and distributing his love to all.No doubt that all creations belongs to Allah but one's belief, one's religion makes us muslims differ from the non muslims. For Muslims to love Allah is to follow the footsteps of our prophet Muhammad, peace and blessing be upon him.He is our messenger and we muslims are connected to him with the finest of feeling and the wisest of intelligence ~ only if you knew!! 
To become a muslim (one who attain light),believes in the Confession of Unity ~ that there is no other god except Allah and Muhammad is the messenger of Allah.Not with only one's tongue but one recites internally with the heart.In one whose heart, Allah has opened to the submission of Islam,follows the light from his lord Allah.This is Allah's guidance, cos He guides whom He pleases.