I gotta agree with those who say it doesn't matter at all, good even great games can exist in any of those formats. Writing, gameplay, gameplay testing (something that no one does anymore,) Mob design, balance, in-game travel... those are important factors. Setting is important, in regards to geography and history adding to and affecting story. But setting as far as game mechanic... naa, it doesn't matter. I could list several great games from each of those categories, and several more that fit none of those descriptions.