Pokemon by nature has a lot of casual appeal though, at least far more then your Metroids, F-Zeros, or Dark Souls. They're simple to understand and get into, has gameplay that is appealing to all different groups of people, and monsters with widespread appeal. Additionally, much of its media appeals to a casual audience as the anime is a merchandising show, Go has huge appeal with those who exclusively play on phones, and toys that kids love to play with. It does have elements that a hardcore crowd can appreciate of course like competitive, but it doesn't change the fact that at its core Pokemon's appeal is greatly owed to its accessibility.