There should be a game called Ninja Manager, where you create a secretive ninja village and manage everything that happens.

You can send ninjas out on recon missions, build brothels to keep the ninjas happy on off days. You'd have to pay special attention to make sure that your ninja village is secretive enough, and shadowy enough for ninjas to have plenty of places to hide. Because, you know, when ninjas aren't out on recon missions they pass the time by sneaking up on each other and going "Gotcha! I could have snapped your neck right there"

You would also have to be careful to include a chalkboard somewhere that the ninjas could write how many times they got each other, and that would determine the head ninja. That, and who is the best at the bi-monthly ninja sand volleyball tournament.

Speaking of the ninja sand volleyball tournament, you'd have to be sure everyone played by the rules and no one was sneaking up and snapping opponent's necks.

Also, I think it's important that a ninja smoke bomb factory is always operational, because if you don't have that, then your ninjas can't say "ninja vanish!" and narrowly escape from trouble. You would have to determine which ninjas are actually the worst at being ninjas, and then make them take one for the team and stay behind at the smoke bomb factory.

More ideas for this to come.

P.S., if you are a publisher that wants to use this idea for your latest video game (Here's lookin' at you, EA), I only request that I oversee the entire operation to make sure that ninjas are fairly represented in the game.