Many RPGs let you play an evil character, but I very often find the implementation of evil wanting. The fact of the matter is that in nearly all cases, playing an evil character amounts to little more than being a psychotic murderer gutting innocents for a few coppers more. Hell, playing evil for material gains is hardly worth it anyway, seeing as the NPCs you help tend to promptly give you Swords of Ultimate Holiness +23 or whatnot for refusing reward, whereas opting the "evil" route and actually demanding compensation for spending nearly all your available resources on slaying that dragon typically nets you a mere fraction of the gold aforementioned sword would sell for.
Now, I can understand why developers would want to steer players onto the righteous path, as the average plot is designed around you destroying some ancient evil or another, but damn, I would love a game that, while having a great story and without falling into the narrative void where most sandbox games tend to dwell, didn't lump those expectations of goodness onto you.
I'd be very interested in seeing a game where moral corruption would be a tempting, slippery slope. Where you would have an actual motivation for parleying with demons beyond the Darkbolt skill or whatever you would normally gain for doing such a thing. Considering that the loading screen will typically tell you that anyone who summons devils will have their souls dragged down to hell when they die, one would think that you'd need something a wee bit more enticing.
What if releasing that dark power burning inside was the only means by which the character could save a loved one? Couldn't a plot be designed where a character could very realistically feel that, hey, Tzeentchian mutations and eternal torment be damned, this is so important to me that I'm willing to take any step to do it?
"Dark Elf @rpgcodex"
Now thats what i want to see in PE but one can only dream...