The problem with evil RPG characters...

[Veldt Falsetto]

I'm usually a self-interested renegade character that ends up saving the world for the fun of it, not evil but yeah.

Playing a truly evil character in an RPG would be great, imagine playing Final Fantasy VII from Sephiroth's point of view, that...would be amazing, though entirely very easy for a while haha

 

[Doclector]

In Skyrim though you are the Dragon Born through fate, but still the Dragon Born regardless. Only you can perma-kill Alduin and stop the apocalypse. I imagine even the evillest of serial killers still have self preservation instincts, it is in your interest to save the world.

But I get your point, in most games this does ruin immersion and it'd be nice if we could have alternating stories depending on play style and alignment. I think Knights of the Old Republic was the worst for this kind of thing (becoming the baddest of the Sith only to still be forced to continue the defeat Darth Malak saga).

I get self preservation, and that most villains aren't evil for no good reason, but the thing is, some of them are. Some of arguably the best villains want nothing but to be evil. The joker, Mr scratch, the list goes on, and in the case of trying to play those characters, it sucks to be all "decorate the bannered mane with the patron's intestines" one minute, and then "Yes, Mr Arngeir sir" the next.

 

[Acier]

I really don't see the problem with it. I mean how many times does the antagonists goal serve the character in any way what so ever? For the Evulz is usually seen as poor justification writing wise, and usually the evil plot is self serving to the villain and would be a detriment to the protagonist, regardless of their morality.