Imagine what would happen if a Final Fantasy game came out that seemed to follow the formula but with one crucial detail changed: Instead of a single person attempting to destroy the world there is a small group of people trying to destroy the world and you control them!
Sure, the game starts innocently enough. Almost like in the original Final Fantasy your first job is to take a little band of heroes and defeat some big boss within the initial half hour of game play.
Unlike other FF games, after the aforementioned villain is brought low by your repeated tapping of the 'A' button there's the little matter of the politics surrounding him. Perhaps there is a dispute over land that this dude confiscated from one group and gave to another diametrically opposed group many years ago. Lord Badguy's iron fist used to keep everyone in check but now that he's dead it's up to your stalwart band of heroes to do the right thing.
And so it goes. Perhaps this initial difficulty is seemingly resolved but one thing leads to another and it isn't long before the game slowly begins to present things in such a light as to make palatable (to the player) the distasteful, the uncomfortable and (towards the end) the unthinkable. At the same time the characters' motives are ever so gradually twisted to allow them to make the worst possible ethical decisions while at the same time making the typical munchkin player feel almost good about it -- perhaps even smug. As with every FF character the individuals in this group start out with the best intentions. Unlike every FF character they are slowly driven by circumstances and their own weaknesses to become as evil and insane as every villain in every FF game ever. Think of it as a subtle "reverse Ultima IV".
As with every Final Fantasy game, the crowning moment is the final battle between good and evil. Too bad your characters -- despite being total bad asses by this time -- are rotten to the core and desperately in need of some knight in shining armor to come and put them out of their (and the rest of the world's) misery. The wise player will probably see this coming, but (if done correctly) most won't get it until their last character has coughed out his last cursed breath and the final cut scene is unreeled.