Man, lame. I hate the special status that some random belief has got in this world. People choose to believe something, it shouldn't be beyond criticism or parodying or whatever
to be fair to your Demon/Dark Souls idea (and I agree), I think every setting ever would make a great Dark Souls/Demon Souls type game. Fuck it, where's my Sesame Street Dark Souls/Demon Souls type game? Tell me you wouldn't play it!
Man Egyptian mythology is just ripe for some amazing settings.
Picture this
Our anti-hero walks into a giant hall, flanks of carved pillars intricately drawn up with heiroglyphics of rich blues, reds, black and whites marching down the left and right side of the room. At the far end of the room and building up toward the ceiling are 42 judges and gods, shadows cast over you menacingly as they point you toward a set of pristine golden scales at the center. Your eyes widen as you recognize the device immediately. Horrific scaled hands grab your arms and legs and spread you down on a small altar before the scales. Golden strips run down the floor woven with gems of every rainbow-like hue.
A robed jackal comes before you with a giant onyx dagger and recites some ancient lost Egyptian dialect; as he finishes, he plunges the dagger into your chest and forcibly removes your heart. It pulses grotesquely as it is placed down upon the scales. A feather floats down from the ceiling and lands gracefully upon the other side of the scale. Immediately the balance of the device falls off, creaking back and forth, finally settling in place as the heart nearly touches the floor. "You are damned for your life time of sin."
They march you into the next room, a giant chasm opens up before you. THE GREAT SWALLOWER, Ammit, massive hippo-like body helmed by the head of a crocodile so fierce and so massive that our anti-heros field of vision is completely consumed. You are kicked off into the abyss, and there the player takes control as you face Ammit in an epic classic God of War battle.
I just described the Hall of Truths and the actual scenario of being judged for the afterlife, but the book of the Dead has some amazing fucking scenarios.
Another description
Yo this game would be so awesome.