My dear friends,
There is only One God. You can call him Allah, God or Yaweeh. He is the same. Even the Hindus& Buddist believe in God (though they do worship also other gods & are not concidered to be religions of the "Book")but they believe also in morality, being good and fair.
The Christian, Muslims and even the Jews worship the same God, but have different ways of interpreting them. That does not mean that God has different standards. It is the people who apply the different standards. And yes, there is Justice in this world. This Justice is applied by the people who live by the way that God likes and are working to "pass the test". However too many people are not concerned by passing the test and believe that the only life they will ever have is here on Earth. That is why they are working so hard on accumulating wealth & power because that is, in their eyes, the most important thing in life. We all know that to accumulate wealth & power is usually done on the back of someone else.... and that means that something unjust has been done. And yes, God will give Justice. But his ways of doing that is misterious and we will only realize later what that Justice was. Remember God will help those who will help themselves. So first help your self and you will get your rewards.
Regards,

Aisha-Taweela