I realized in a very early stage in life when I first heard people talking about the purpose of life, that they must not disbelieve in their Creator, for without there being Him, they would not have a purpose, or they would not be asking about it, and they verily would not even exist. The purpose of life is known only by the giver of life. I searched half my life how to worship Him, because I realized I love Him more than anything else can be loved, and nothing deserves the love that is due to Him. I found His Religion by searching thus, and by asking Him to give my life whole for Him and go where He wants of me, and how to best worship Him, so He guided me. So I`ve now been a muslim for eight and a half years since then, may Allaah be praised for that, and it has been confirmed in The Book of God:
The pursose of life is for all of you what I knew it to be for me (maybe your souls forgot):

And remind, for indeed, the reminder benefits the believers.
51:55
And I did not create the jinn and mankind except to worship me (Alone).
51:56
I do not want from them any provision, nor do I want them to feed Me.
51:57
Indeed, it is Allah who is the [continual] Provider, the firm possessor of strength.
51:58

If you are doubtfull that Allaah is your Lord, and there is no god but Him, and that Islam is His Religion, and that He sent Muhammad -peace and blessing from Him upon him- as a Messenger onto you, so that you should follow Him in order to find your way back to your Lord, and that He may accept you and forgive you, then please listen to The Word of Allaah as it was revealed, and ask your heart: "Is this not The Speach of my Lord?":

Www.all-quran.com

Thanks for your comprehensive reply.I agree with you but a question comes to my mind that other religions were also created by the creator, are those not true religions. Worshiping God/ Allah/ Creator may be part of aim of life of humans but doing good to other humans may also be another part of the aim.

Humans created other religions with Satan's influence, but God created only one. (Colossians 2:8; Matthew 7:13,14)
The greatest commandment in the bible is to love God with all our heart, soul and mind and the second is to love our neighbour as ourselves. (Matthew 22:37-39) In order to do God's will, we cannot ignore these two commandments.

What a great question. Genesis 1:28-30 tell us that god originally commanded us to fill the earth. He gave Adam & Eve a model to follow in the garden of eden. We were supposed to transform the entire earth into a lush & wonderful paradise. This was our original purpose. Needless to say, this had to be put on hold when they were expelled from the garden of eden (Genesis 23:,24).

During this interim period, god has given us a new purpose/assignment found at John 17:3. This new assignment is to help everyone gain accurate knowledge of God, and his son Jesus.

Isaiah 55:11 tells us that what god says word will "not return to me without results" (NWT). With this in mind, we will return and fulfill gods original purpose for us to transform the entire earth into a paradise, like the garden of eden. This will happen soon when god and his son resume direct rule of the earth. This will be a great time for all the righteous as described at Revelation 21:3,4 (NWT)
With that I heard a loud voice from the throne say: “Look! The tent of God is with mankind, and he will reside with them, and they will be his peoples. And God himself will be with them. 4 And he will wipe out every tear from their eyes, and death will be no more, neither will mourning nor outcry nor pain be anymore. The former things have passed away.”

Thanks. I am grateful.

There is only one Religion of God, and Jesus never spoke of Christianity, nor did he say he was one of them, nor did he say in the name of the father and son and the holy ghost, nor was his name Jesus Christ. If you really act on what you preach, and obey him, then leave your religious prestige, and be ready not to argue against the Truth from God when it reaches you, as most christians are not. You will find His Religion, if it is what you seek. You will come to know the Truth, if it is what you sinserely ask from Him. The Devil is working hard, and you can see in the world they are all gathered against only one particular religion. Doesn`t that make you wonder why on earth would Satan keep telling lies about Islam and muslims and sending armies of the world to kill them if they were one of his own?