We chat about videogames and videogame accessories.

I would argue that the main problem is the Lowest Common Denominator, to wit: the people who want quality games that go bold new directions are substantially outnumbered by the people who purchase a game solely by virtue of "whoa those guns are cool! ZOMBIES TOO LET'S DO IT" There's a sort of echo chamber effect (as there is with a lot of things) because when you're a Yahtzee-watching, game-dissecting connoiseur type you tend to discuss video games with similarly high-falutin' individuals, thus getting the impression that obviously the industry should be following what is clearly the majority opinion.

Then again, part of that might be said to be a vicious circle, in that established franchises are proven to do well, thus get more marketing; the combination of the marketing and brand recognition means more casual enthusiasts buy them, not bothering to research their actual quality (which, as mentioned, many mainstream game publications don't exactly help with in the first place); which in turn means that the established franchise remains more successful than new IPs.