If you are looking at which religion show the most increase in adherents, Christianity is the fastest growing religion in the world.  To ask why, is very reasonable.  It doesn’t really fit into my discussion here, but I like the answer so well I am posting it anyway. 

I think the best answer for this was written by Dinesh d’Souza in a book call “What’s So Great About Christianity” and he is actually quoting Randy Alcorn.  I’ve included it below, but if you want to read more directly from the book, click here.

Rev. Randy Alcorn, founder of Eternal Perspectives Ministries offers two creation stories and asks whether it matters which one is true. In the secular account, “You are the descendent of a tiny cell of primordial protoplasm washed up on an empty beach three and a half billion years ago. You are the blind and arbitrary product of time, chance, and natural forces. You are a mere grab-bag of atomic particles, a conglomeration of genetic substances. You exist on a timey planet in a minute solar system in an empty corner of a meaningless universe. You are a purely biological entity, different only in degree but not in kind from a microbe, virus, or amoeba. You have no essence beyond your body, and at death you will cease to exist entirely. In short, you came from nothing and are going nowhere.”

In the Christian view, by contrast, “You are the special creation of a good and all-powerful God. You are created in His image, with capacities to think, feel, and worship that set you above all other life forms. You differ from the animals not simply in degree but in kind. Not only is your kind unique, but you are unique among your kind. Your Creator loves you so much and so intensely desires your companionship and affection that He has a perfect plan for your life. In addition, God gave the life of His only Son that you might spend eternity with Him. If you are willing to accept the gift of salvation, you can become a child of God.

Now imagine two groups of people – let’s call them the secular tribe and the religious tribe – who subscribe to these two world views. Which of the two tribes is more likely to survive, prosper, and multiply? The religious tribe is made up of people who have an animating sense of purpose. The secular tribe is made up of people who are not sure why they exist at all. The religious tribe is composed of individuals who view their every thought and action as consequential. The secular tribe is made up of matter that cannot explain why it is able to think at all.[1]