So really how authentic can we make elves? what accent should they use?
Oh wait none, because they don't actually exist, the developers are using the only approach they can and that is fine for me because it is their world that they are creating, not recreating medieval earth.
@OP,
I think this guy up here pretty much says it all. I think the premisse of what you deem to be 'authentic' is almost an oxymoron, because in a fantasy world is impossible to have an actual frame of reference, therefore the word 'authenticity' seems moot. But I get the feeling that the word is not even the problem, I think you meant just a general feeling of the accents being somewhat off, and I can respect that point (even tough I disagree wholeheartedly). More than that, you'd be right to point out some general resemblances (not only in terms of accent, but also names and sometimes even cultural traits) between bretons and french, for example. We can't escape some level of reference to our real world, be it Skyrim or any other work.
That being said, to be even more honest, I think it's arbitrary to equate races other than humans (Elves etc.) with accents of smaller, less mainstream countries. The problem imho seems to be the fact that american accents in general seem too commonplace, certainly because of its overuse, due to the fact that american culture is still so prevalent all around the world. But some good examples of well done american accented voices are still out there (which I know you're not disagreeing, I understood the point of your thread).
On that note, I'd ask you finally, can you give me some examples as to which voices annoyed most and why they seemed out of place? This seems like an interesting discussion nonetheless.