What We Could Do
There’s nothing wrong with Edenian moral choices per se. Sometimes you don’t want to have to think too hard about the gut-wrenching compromises of the real world. Sometimes you just want to see the forces of good triumphantly riding over the forces of evil. And that’s okay!
The only problem with this system is that it keeps getting shoehorned into places it doesn’t belong. Is your game trying to say something about the nature of good and evil? Maybe this sort of choice mechanic is called for. Is your game pretty much the same regardless of what choices you make? Maybe leave it out.
The most frustrating aspect of this sort of system is that there is generally no incentive to mix moralities. As in Infamous, the best powers and rewards are reserved for those who do the right thing every time or the wrong thing every time. This eradicates the meaning of every choice but the first: do I want the Good ending or the Evil ending? There is no room for moral growth or change, no reason to play as anything but a caricature and no change to explore nuance. It is good or evil, Pepsi or Coke.
That doesn’t mean that there aren’t things that haven’t been done yet. Most Edenian systems assume a rough parity of power between good and evil. Each path may have unique abilities, but each path has is equally viable. Dishonored takes a good step by having moral choices substantively affect the game world, but we can take it further.
One way to do this would be with a simple power imbalance. For example, a “Right is Might” game where taking the moral path is rewarded with more powerful upgrades than their evil equivalents. Good players can trample the wicked beneath their heels, while evil characters have to sneak around in the shadows. Evil powers are generally portrayed as the more destructive – that’s an assumption that can be subverted.
We could also subvert this in the opposite direction. Bioshock's ADAM dilemma could have been interesting if sparing the Little Sisters actually reduced the player's power. If the "good" choices required actual sacrifice, making the game more difficult to complete, the moral choices would have had more impact.
I would also love to see a game that takes the idea of a “curse” to its extreme Genesis-esque limits. Perhaps a system where committing immoral actions gives the player permanent debuffs which cannot be removed, or releases plagues of new monstrous enemies into the world. "Cursed is the ground for your sake... Both thorns and thistles it shall bring forth for you," to paraphrase Genesis 3:17-18.
Dishonored does something similar, but I’m not talking about increased numbers of existing enemies, but rather more varieties of more aggressive enemies that actively lay waste to the game world. Maybe this means formerly friendly animals/NPCS become violent and antagonistic - herbivores become carnivores.
Above all, I would like to see Edenian games that treat good and evil as something more than gutless abstractions. Far too often, good is some rootless concept of fluffy niceness. I want a good that stands for a clearly defined moral concept. I don’t want an evil that is a vague black-and-purple cloud of not-niceness, I want evil with cosmic consequences.
The way for Edenian morality to be good again is to take it back to the Garden. The tree of the knowledge of good and evil is polarizing in so many, many ways beyond the obvious good and evil bit. Is it good of God to give Adam and Eve this test? Is cursing them to die an appropriate response? Even if this story seems irrational to some, it has a memorable texture that sparks discussion and controversy. There is no Tapioca of Good and Evil in the Garden, but a fruit with bite.