If a game it’s supposed to have a story, then it shall be first, if you develop the story you need the characters, after that the gameplay, the gameplay needs to be developed in what the story needs, or you are going to have a ludonarrative dissonance problem in your hands. After you know how the execution it’s going to be, you can invest in the composition, the art style, timing, cinematics, music, etc. If a game it’s supposed to be “fun”, then the gameplay shall be first, that said, if a game developer really want to express something the gameplay should be developed to be the bridge between what you want to say and the player, and so having the story first it’s a must.