Wall of text incoming:
The key thing to think about here is that the gaming industry is exactly what it describes; it's part of the entertainment industry, the primary goal of the industry as a whole is to develop products that will return a profit. Now, generally speaking, AAA games sell much better than their indie or small firm counterparts (Some may argue that it's several orders of magnitude higher). In order to make these games however, you need an astronomical principal investment averaging anywhere within 15 - 100 million USD. As you might have guessed, most firms don't have this kind of money lying around, so they need to convince investors and publishers to provide them with this principal investment. To convince a 3rd party investor or a publishing company, you need to prove that your project is going to provide them with a decent return on investment, else they aren't going to give you the time of day. The best, if not only, way of doing this is to show them how well the target demographic has responded to games of similar mechanics. You have to remember that these people usually aren't the "Games are art" types. They are not here to "further the industry as an art-form" or "transcend the current notions of gaming," they're here to make a profit and further their brand, plain and simple. They usually aren't going to want to fund your SCP: Containment Breaches or your Slenders because, from a financial point of view, they're extremely risky investments. There aren't many people out there that are willing to risk that kind of money on something that doesn't show much promise for a positive return on investment, let alone crashing.
If you want games with unique gameplay, you're either going to have to stick to the indie crowd, or somehow convince a nation of people that the games that they love and enjoy suck. That being said, the indie gaming field is slowly getting better. Especially with medium-highish power engines being accessible to developers, often cutting the need for a dedicated programmer entirely. But the industry is still very young, it's hard to tell what will come of it.
 Somewhat hard to find decent data on this. Best estimation could come up with.
 Assuming you put these games on a decent level budget