If one reads history of religion there is one common aspect which gives reason for establishing a religion. Wise persons found the rules of religion prevailing at that time are inadequate to deal with a society in a particular place at certain period of time. So new rules are formulated taking in to account the prevailing situation (This also means rules are relative to surroundings. If conditions change rules do change. This is the reason each of the nations on our earth have different constitutions and many rules different than other nations.)

This is the reason why different religions were born in different period of time at different locations on the earth. There have to be similarities because the fundamental principle of every religion had been and is nurturing brotherhood among among members of society. This leads to a solution for peace.

Let every nation have a religion named after that nation. Constitution, Laws and regulations of that nation shall be religious rules. Full freedom shall be given to every citizen to worship in any manner as long as it does not disturb peace of other citizens. If any one migrates from one nation to other he/she must accept the religion of the nation to whch migrated.

In my opinion this shall bring peace to whole world.

__________________
Brotherhood is the only necessity of the mankind, religion is not at all necessary for survival of human race. Let religion be limited to worship alone and that to in private places. Read more Here or Here or Here