In recorded history, Hinduism has been the most popular for the longest period of time. It is the world’s oldest religion with 79% of adherents in Nepal and 79% in India. http://www.adherents.com/largecom/com_hindu.html Earliest known Hindu scriptures are the "Vedas". Vedas describe the religion of Aryans, who invaded India around 1500 B.C. Hinduism today has 900 million and ranks at 14% for adherents. http://www.adherents.com/Religions_By_Adherents.html#Judaism Edit- Perhaps I am wrong but I believe Egyptian mythology wasn't the most “popular religion" for the longest period but the civilisation of ancient Egypt lasted longer according to what we accept as recorded history. Under the Pharaoh they had all kinds of gods and goddesses. To ancient Egyptians the term 'religion' didn’t exist. Their gods and goddesses were part of everyday life and they had many deities. Dead kings and queens were assured of life and sustenance in the hereafter. That alone, in my opinion would not have made it the "most popular" over the longest period of time. Hindus trace their origin to the ancient Vedic culture at “least” as far back as 2000 BCE. Ekam Sat Vipraha Bahudha Vadanti - Truth is One, though the sages know it as many. It is said that Islam is actually not a few hundred years old ,but in fact Islam is the oldest long before man set foot on earth. Also that Prophet Muhammad was not the founder of Islam. He was the last and final Messenger of Almighty God. The Qur’an is the only religious book on the face of the earth, which has maintained its purity and authenticity. Islam is not a man-made religion. Today it's not the most popular but ranked near the top as far as a belief system.

Here is the current "Top 20" chart rundown: Christianity 2,039 million 32% Islam 1,226 million 19% No religion 925 million 14% Hinduism 828 million 13% Chinese folk rel. 390 million 6% Buddhism 364 million 6% Tribal Religions 232 million 4% New religions. 103 million 2% Sikhism 23.8 million <1% Judaism 14.5 million <1% Spiritism 12.6 million <1% Baha'i Faith 7.4 million <1% Confucianism 6.3 million <1% Jainism 4.3 million <1% Zoroastrianism 2.7 million <1% Shinto 2.7 million <1% Taoism 2.7 million <1% Other 1.1 million <1% Wicca 0.5 million? <1%

the most poplular one would be the wrong one - the ecumenical movement-because it satisfies the flesh and lets people continue in their sin> Jesus said "If the world hate you, ye know that it hated me before it hated you." (John 15:18) He said that the world would hate him because he comes to reveal sin and rebuke it! Jesus is not popular if you take him for what he really is .If you change things around and distort the message as so many do, then it will be popular.I'll follow it as it is! and have Gods blessing rather than his wrath!

In terms of numbers Christianity is with around 2.1 billion. Followed by Islam 1.3 billion and Agnostic/Atheist with 1.1 billion

Popular or most pratised? About.com suggests that popular means most adherents: http://geography.about.com/od/culturalgeography/a/popularreligion.htm Christianity is the largest religion: http://www.adherents.com/Religions_By_Adherents.html Here is another answer I found: In terms of numbers, Christianity is the world's most popular religion, with approximately 2.1 billion followers. This includes just over a billion Catholics, about 350 million Protestants, and the Orthodox and Anglican faiths. The religion statistics resource Adherents.com hosts a fascinating pie graph that breaks down the world's major religions by population. Islam is the world's second-largest religion, with roughly 1.3 billion followers -- including 940 million Sunnis and 170 million Shiites, as well as those belonging to other Muslim faiths like Sufism. Depending on your resources, the third-largest group is either Hindus or atheists. Both hover just under the billion mark. Traditional Chinese religion (which is related to, but distinct from, Buddhism) takes fourth place with 400 million, and Buddhism trails close behind. The Hindu organization Om Sakthi hosts a nifty timeline tracking the origin of the world's religions. Islam's rapid growth is impressive, especially considering it's one of the younger major faiths (it was founded in A.D. 622). Right now it's considered the fastest-growing religion in the world. - http://ask.yahoo.com/20060120.html

Christianity has the largest number of people , but in general we are also the least devout and practising of the major religions.