The latest games are usually evolving from tried and true templates. It's only once in a while that a revolution occurs that spawns something truly original. No fault of the game designers, it's pretty damn hard to come up with anything new, and impossible to not recycle anything. If any game developer wishes to remain in business, that's just the way it is.
Fred_Bonaparte is right. Indie game developers are the ones who can still experiment with new ideas. Most large game developers have to streamline their game development process to maintain their productivity. Any committed research would have to yield some form of financial return in the long run, otherwise a lot of money can be "wasted".
The larger the company is, the higher the operation cost. They can either decide to try doing something new and risk facing a loss or stick to the old roots and churn out numerous similar products to stand a higher chance of remaining in profit. That's why many franchises are developed (Game 1, Game 1: Expansion, Game 2, etc). Each new installation of the same title has the benefit of drawing from an already present fanbase, increasing the chances of the next commercial success and at the same time, reducing the production overhead of doing another thing from scratch. It's a win-win situation.
