There are plenty of ‘endless runner’ games available on the App Store – enough to encourage some to think that the genre is done-to-death. So would it make sense to create another if there are many others like it? Of course! If your plan was to create an endless runner you shouldn’t change that because you think there are too many games like it already. Of course you should be aware of what already exists – but resist the temptation to change your game based on what is most popular at any given point in time. The more you allow your game to be influenced by others – the less interesting and personal it becomes. As a creator the audience is interested in your take on things – this is what gives your game character and makes it unique. If you keep things personal you will make a valuable contribution.