In a previous post, I was upholding that if you want to make a game then you must be the first one who believes in its success. So, I said that you might be the one who funds the project. There is a special case which deserves a dedicated treatment: the crowdfunding.
The crowdfunding might be the right solution if you can’t obtain a funding. Maybe you are targeting a niche, so your project might not be interesting for an investor; but it might still be interesting for a lot of small investors, the crowdfunding. So, if you have a great idea with a doubtful economic value you could consider sharing risks among many people who believe in the project like you.