Most RPGs or RPG-like games, at least the kind I play, playing evil means you’re just Chaotic Stupid. Case in point: punching the reporter in Mass Effect (on camera, no less) just makes Shepard look like an unprofessional meathead. Far more satisfying to destroy her with words on her own show. On the other hand, I always headbutt the krogan; that’s just a smart play vs the krogan. It’s also smart to tase the gunship mechanic.
In contrast, I’ve no compunctions being evil in grand strategy games. I’ll happily kill my wife if the bitch won’t give me any sons. Forging documents, poisoning a rival, exploiting the natives, committing genocide – all options are on the table.