The Greatest religion in the World.
Christianity !!!!!
It penetrates every part of human's civilization, contributes to human race more than anything else.
Yes I think we should take a moment to reflect gratefully on all that christianity has given us:
http://www.dimensional.com/~randl/racking.htm
http://shanmonster.bla-bla.com/witch/torture/index.html
http://atheism.about.com/library/weekly/aa102198.htm?once=true&
And lets not forget that good christian who laid the foundations of Nazi germany:
"to set fire to their synagogues or schools and to bury and cover with dirt whatever will not burn... I advise that their houses be razed and destroyed... I advise that all their prayer books... in which such idolatry, lies, cursing, and blasphemy are taught, be taken from them... that their rabbis be forbidden to teach henceforth on pain of loss of life and limb... that safe-conduct on the highways be abolished completely for the Jews... that all their treasure of silver and gold be taken from them... But if the authorities are reluctant to use force and restrain the Jews' devilish wantonness, the latter should, as we said, be expelled from their country and be told to return to ... Jerusalem where they may lie, curse, blaspheme, defame, murder, steal, rob, practice usury, mock, and indulge in all those infamous abominations which they practice among us, and leave ... our Lord the Messiah, our faith, and our church undefiled and uncontaminated with their devilish tyranny and malice." (Martin Luther, On the Jews and their Lies, 1543, cited in [SH248]
http://playground.www1.50megs.com/badboys.html
My personal all time favorite quote from a christian, because it seems to express true christian philosophy:
"Kill them all, God will recognize his own." (Arnald-Amalric, 1208,when asked by the Crusaders what to do with the citizens of Beziers who were a mixture of Catholics and Cathars)
http://www.geocities.com/atheistdivine/badfruits.html
So if by greatest religion you mean the greatest threat to human life, happiness and peace, I would have to agree.