Sister, first of all. The religion of Adam, Noah, Abraham, Moses, Jesus, Muhammad (peace be upon all the prophets) was to worship our Creator Alone sincerely, and not to associate partners with Him in that worship.
Now we know that the majority of mankind believe that this universe wasn't created by itself. Only a minority are atheists.
This was in another post:
Let's start off with the fact that the majority of the world believes in a God, or 'Higher being.' The difference between islaam and all other faiths is that instead of just recognising that there is a God, we believe that the Creator created us with the purpose of submitting to Him, worshipping Him alone sincerely without any associates.
These associates can be stone idols, it can be humans (or human legislations) it can be a person's desires etc.
Islaam call's to the worship of God, known as Allaah in arabic. If you're confused about why God is Allaah in arabic, realise that people from spain call God - Dios, the french call God - Dieu etc. Therefore we call God, Allaah in arabic.
Allaah has sent messengers to convey the same message of calling to the worship of God since the beginning of time, since Adam (peace be upon him) the first person to ever live. All the messengers came to call to Allaah's worship, and this is the purpose of our creation - to worship Allaah, without no associates, so no idols, no humans, no law which opposes the law which Allaah has revealed to His messengers.
We as muslims believe that Noah, Moses, Jesus, Muhammad (peace be upon them all) were prophets. There have been a total of 124,000 prophets that have come to mankind to call to the worship of Allaah Alone. However, the majority of mankind has fallen astray, because they do believe in a Creator, but they reject the fact that He should be worshipped alone.
Any deeds we do, we do them sincerely to gain Allaah's Mercy, and if we gain it - we will enter the eternal paradise which all the prophets have called to also. However, if someone rejects the worship of the One God - without any associates, they will be punished in the hellfire. This is the only sin which God does not forgive, why should He, if the person is saying that a stone is God? Or a human is God etc.
We all will die and be raised back on the day of recompense, when Allaah/God will judge between us on all that we did. No-one will be judged unfairly because Allaah is the Most Just. Allaah can bring the dead back to life, the same way He brings the dead land back to life by sending down rain.
If you feel that God is being unfair to His servants by punishing those that associate partners with Him, then the justice for this will also be balanced out. Allaah will ask those who associated partners with Him to ask the one's they worshipped for reward. So if someone worshipped a stone idol, they will ask that for recompense on the day of judgement (obviously the stone won't be able to do anything.) If someone worships a human, even if the human is pious, the person will have to get their reward from this human [but obviously everything is dependant on the Creator.] The one's who worshipped God Alone, sincerely without no associates - they will be rewarded by Allaah, the Exhalted with an eternal paradise where they can have all that they desire, and more.
If anyone feels that it is unjust, then they have to stop being unjust to their own Creator. If Allaah created man so he should worship Him, then why worship the stone idol, or why worship a human when you can turn towards your Creator?
Allaah Almighty knows best.
If you have any questions, please don't hesitate to ask insha'Allaah. :)