"... draw on your face with my pretty knife
I want you to know what love is." - What Love Is, Rocket from the Tombs
"Evil" is like "Punk rock". A label that is vague, poorly understood, and ultimately illusory. Both are seldom portrayed honestly; we are generally shown only the extreme, and unlikeable stereotypes of each. An evil character won't burn down the world, because then there won't be anyone to make his breakfast tomorrow. [But it had BETTER not be cold this time!!!]
Part of the problem is that 'Evil' 'Crazy'. Someone needs to sit Devs down and explain the difference. You can have the Light side, the Dark side, and the Dark Side of the Moon. They aren't mutually exclusive, but you shouldn't substitute one for the other. I'm having a ball playing the old title "Vampire the Masquerade:Bloodlines". In the game you can technically be a good-ish or evil-ish and even an insane vampire. I'm playing the insane vampire, and its funny because the dialogue is just not insanity. It's more like a middle-aged professor of classics got completely wasted at a party of the classics department people, and then decided to write "crazy" dialogue. It ended up being just a lot of metaphor, so the character would seem to be incoherent when she is actually just using a strange "poetic" language. Then there are moments when you might do things that sound evil, but someone sent you to do it.
For the OP, if you haven't I recommend trying the Agent in SWtoR. [It's FtP, but I really object to the client size. They don't need to put two full intro movies on my HDD!] Before long I quit because of the grind, and the player-based market makes crafting impossible. What I enjoyed *enormously* was the dialogue options to tell this whiny NPC that "I don't give a frozen toydarian turd about your horribly polluted environment! Can't you see that I am *the* Player Character? Don't you know that I have much more important ... um ... things to do to other whiny NPCs that are far more entertaining than listening to you!" That's not even a particularly 'evil' moment either, its just a great dialogue option. There are quite a lot of quests in Oblivion where I didn't really want to do them, but they benefited me in an other way.
I could make a better case that the normal 'good' Player Character is suffering from some kind of brain damage. He just blithely goes around killing things and collecting stuff just because some absent minded twit told him to. There's a game on Steam called Mars:War Logs. I do not recommend it. The protagonist is this tough guy who succeeds in breaking out of an internment camp, and incidentally killing the warden in a cutscene. In the next town he turns up, this thug of a man goes right back to doing silly fetch quests for anyone that can whine on his frequency, when he could hire himself out as an enforcer of some kind. What I'm saying is that its not just that there is something wrong with 'game evil'; 'game good' is pretty bizarre as well.
And there is a very good reason not to do the "bad" Eve extraction in the Bioshock series. Doing that gets Little Sister all over your designer shoes. Nobody wants to spend their Sunday afternoons scraping Little Sister out of their boots. Not to mention that its pretty awkward in the convenience store. I just wanted a gallon of milk, and I think I was out of baking soda, but this lady notices that I've got Little Sister all over me. She won't ring up my purchases and let me get on with my business. She's gotta go on about 'did I know what her name was', and 'did she live around here' before, and 'who were her parents', and other stuff. Well, you know, I wanted to shut her up too, but this was kinda too public for me. I didn't need the milk that bad, so I left. She coulda had the sale if she'd kept herself to herself.