The casual games industry, for better or worse, is beholden to game distribution websites known as portals (or 'evil portals,' depending on who you are). Each of the portals carries a large catalog of games that is fairly unique, but regardless of this fact, casual surveyors of the industry find the portals to be about as dissimilar as the games they carry -- which is to say, not very.
The attack laid at portals' feet -- that they are essentially clones of each other -- has some merit, but it is more a case of the portals using a format that works well to compete for the same customer than anything else. While it may seem strange to be similar to your competition in order to compete with them, it shouldn't be too surprising. Consider grocery stores, for instance. Most stores are laid out in a very similar fashion and carry essentially the same products. When you go into a grocery store, you expect that they'll have cereal -- and that it won't be located near the butcher shop. The shared layouts used by different grocery stores help new customers feel comfortable when they walk in the door, but still allows the store to compete for the customer in other ways, such as discount programs...
