“You're basically killing each other to see who's got the better imaginary friend.”
“Religious wars are basically people killing each other over who has the better imaginary friend.”
There is no known basis to attribute this saying to Napoleon. It is found (unattributed) in a Usenet post from July 1999 https://groups.google.com/forum/message/raw?msg=soc.penpals/QIUrpkacWyE/FbCj7pij5WwJ.
Misattributed
Help us to complete the source, original and additional information
Napoleon I of France 259
French general, First Consul and later Emperor of the French 1769–1821Related quotes
CC Presents: Richard Jeni, aired 5 May 2002 http://www.comedycentral.com/video-clips/6kmgg7/comedy-central-presents-brought-up-catholic.
Comedy Central Presents (2002)

“All religious wars are about people arguing over who has the biggest invisible friend.”
Many unsourced variations are attributed to Arafat.[citation needed] The actual origin is Richard Jeni.
Misattributed
Source: http://www.gdargaud.net/Humor/QuotesReligion.html
Source: The Stone That Never Came Down (1973), Chapter 23 (p. 180)

La guerre, c'est un massacre de gens qui ne se connaissent pas, au profit de gens qui se connaissent, mais ne se massacrent pas.
Bizarre, issues 24-31 (1962), p. 102
This apocryphal quote from Paul Valéry is never precisely sourced: neither on the internet nor in the works we have consulted. See: https://www.guichetdusavoir.org/question/voir/52650

Source: The Letters of Dorothy L. Sayers. Vol. 1, 1899-1936: The Making of a Detective Novelist

“In a war of ideas it is people who get killed.”
Unkempt Thoughts (1957), p. 21, http://books.google.com/books?id=NTtiAAAAMAAJ&q;=%22In+a+war+of+ideas+it+is+people+who+get+killed%22&pg;=PA21#v=onepage
“In the end, it is ideas for which people kill each other.”
Introduction, p. 11
Think (1999)