Each religion claims to be the 'correct' one. None of them have any evidence (and if they do, it's always just the same evidence twisted to fit their views).
How is it that this can be? A Christian will tell a Muslim that by being Christian they will go to Heaven. A Muslim will tell a Christian that by being Muslim they will go to Heaven (the same Heaven of course). Both may claim to have spoken with God and have first-hand knowledge that their religion is the correct one to follow. But, there's no evidence to prove that either of them spoke to God, so who is a non-religious person supposed to believe? They are basically left to believe the person with the most resources to convert them. The success of a religion all comes down to whether or not the people dying can convert enough people over to fill in their place. If the number of people dying (leaving the religion) is more than the number of people being converted or born into the religion, then the religion will fail.
Those born into the religion are easy numbers to add, because they are brainwashed from such an early age that it is not difficult to "convert them" (because they essentially are born with no religion it is like a conversion). The older someone becomes, the more work it takes to convert or brainwash that individual. The more money that a religion can spend, the easier time it will have converting others to join. Thus we see the success of Christianity--the primary religion of the U.S. and other industrialized countries.
Many [hardcore] Christians (especially Evangelists) take "mission trips." The idea is that they preach to people about God, and His CHRISTIAN glory and then help the poor village people build a house or clean up after a storm. The reality is that these Christians are offering their services (badly needed by the poor village people) in return for the promise of the village people professing to be Christians and to spread the word of God. Something like: "say you believe in MY god, and we will build you a house or help you with some other service which you desperately need to survive." The religions with the most money are those that can do this sort of thing the most. An equation basically comes out that the more money your religion has, the more likely it will be able to convert a large number of people.
If a religion attempts to measure its success by successful conversions (which many do), then it becomes quite clear that wealthy religions are successful religions. Religions are financial organizations, plain and simple. This idea, however, goes against some of the primary teachings of many religions, for certain Christianity.
How do religions justify the use of money to convert people? Using ANY money to convert people in the end becomes a way of paying people for joining your religion--which is okay if you accept religion as a financial organization, but down-right heathen-like if you actually believe the beliefs you profess to believe.
Jon