See how the major religions expand in this multimedia presentation at Maps of War. Unfortunately it covers only the three Abrahamic faiths and two faiths originated from the Indian sub-continents. Other faiths like Jainism, Taoism, Sikhism, Bahai’ Faith are all not included. Thanks to Lynette for this link.
People are the boss 
Amusing how Christianity spreads so easily over the wastes and tundra of Canada and Russia. It leaves a false impression.
It is highly simplified and ‘maps’ only the political boundaries, not the thought boundaries