I've been toying with the idea of a game that handles the 'black and white' or 'good and evil' stereotypical morality choice and actually manages to make it an interesting concept rather than the blase interchangeable meaningless choice or merely determining the flavor of super powers you get.
This is what I have envisioned: The game would be an RPG, your character would be a person who's hometown is on the verge of being overrun by an invading demon force. Your town and the neighboring towns and cities are the last remnants of humanity. Things are looking dire. You investigate some old ruins looking for a possible answer, find a talking spirit that promises the answer, and it endows you with the ability to absorb other people's power. Not the invading demon's powers, those don't do anything, only those of your fellow human countrymen.
Mechanically speaking, you have your typical RPG leveling you know and love, but the only things that give experience are other humans, of which there are only a finite number in the game world at this point. Ordinary people provide a little, but there's a caste of warriors called the 'blessed ones' that have devoted their whole lives to worship and self-perfection, and have been granted special power and ability from god. These are the last champions protecting the human race, but only about a dozen are left existing and they are badly stretched out just trying to defend their own sections of the border between human and demon territory.
However, just trying to hang back and defend is a futile task, the demon force is completely inexhaustible, and no matter how many are defeated in battle, they return the next day and in greater and stronger number than before. There'd be a timed element to this game, where you can't linger and take your time, the enemy is at the gate and you have to muster your strength and attack them at their heart. The longer you take in the game, enemy demons get stronger and more numerous, and depending on your actions the borders to human's territory will get pushed in and innocent people will suffer.
So, seeing these very powerful Blessed Ones be unwilling to attack and end the scourge once and for all, it seems like only the responsible thing to defeat them in combat and take their power to do it yourself. However, defeating them leaves the territory they were inhabiting completely undefended unless you stick around and defend it yourself, which is very often not feasible. If you're able to defeat all the demon lords and close the gates to the demon dimension, then humanity will be saved completely, and if a few people have to die as the means to that end, then so be it. The spirit you meet at the start is also like a 'devil on your shoulder' type of character, hanging around you and letting your know just how much more powerful you could be by strangling it outta someone else.
Now, the good and evil part comes in, is that it's perfectly possible to beat the game without killing any humans whatsoever, but it requires immense tactical skill in combat and a lot of traveling through the various towns and cities, picking up allies by doing quests, accumulating wealth by being a merchant and buying/selling between the various city-states, using that wealth to attract more allies with money/food/weapons/whatever, and currying favor with the Blessed Ones who will offer you their assistance if you prove your ability in battle and your trustworthiness. Completing the game by killing no humans and minimizing casualties earns you the best ending and would be prized for being the most difficult ending to get, and there'd be an equivalent bad ending for being the last, and most powerful, human left standing. Plus lots of grey endings for varying degrees of how many humans you personally killed and how many are left alive.