Islam is not the name of some unique religion presented for the first time by Prophet Muhammad (pbuh) who should, on that account be called the founder of Islam.
The Qur’an states that Islam – the complete submission of man before his one and only Unique Creator – is the one and only faith and way of life consistently revealed by God to humankind from the very beginning. Noah, Solomon, David, Abraham, Moses, Isaac and Jesus – prophets who appeared at different times and places – all propagated the same faith and conveyed the same message of Tawheed (Oneness of God), Risaalat (Prophethood) and Aakhirah (the Hereafter). These prophets of God were not founders of different religions to be named after them. They were each reiterating the message and faith of their predecessors.
However, Muhammad (pbuh) was the last Prophet of God. God revived through him the same genuine faith which had been conveyed by all His Prophets. Since there was to be no messenger after Muhammad (pbuh), the Book revealed to him (i.e. the Qur’an) was preserved word for word so that it should be a source of guidance for all times.
Verily, We have sent down to you (O Muhammad (S)) the Book (this Quran) for mankind in truth. So whosoever accepts the guidance, it is only for his own self, and whosoever goes astray, he goes astray only for his (own) loss. And you (O Muhammad (S)) are not a Wakeel (trustee or disposer of affairs, or manager) over them. (The Noble Quran 39:41)