The we're a relatively small party of people and we're here to save the world theme is prevalent in the FF series as a whole. Each new game brings a different resistance faction/small group of chosen ones/etc., a new planet, and a new evil empire/self-proclaimed supreme being intent on cleansing the planet/etc., but the most basic premise is the same.

I've always believed the FF title to be symbolic in that 'Final Fantasy' refers to the last big adventure to save the world, relative to each respective game.