Interesting. I see demon as dark, not evil. Devil's though I see as evil.
(Note: Hades and the Devil are not one in the same. The Devil is a construct of several mythological figures or he is the absolute Devil (Anti-God) of christian religion, depending on your personal religious perspective.)
I think because the Devil is strictly a construct of Christianity that when referenced alongside that, "The Devil" is evil by that value systems description. Although because it's strictly a christian thing there really are no devils. Just the one Devil. So, it can't even considered a fantasy race.
If you were to recreate it as a fantasy race of "devils" then there is little reason that it couldn't be something entirely different and have completely differing values/morals. You could make them flower loving, non-violent, two foot tall creatures if you wanted to.
I feel that's the biggest flaw with this entire thread. There is no good to use race for fantasy/Sci-Fi settings of any kind. Each race is usually something you can completely rewrite and make your own. Limiting yourself when most "known" races have wide and varied mythology anyways seems kind of silly to me. Unless you really happen to like the very specific aspects of one very specific race from one very specific set of stories. Then there needs to be qualifiers to the reason for choosing any specific race.
The topic would do better as a question of what physical traits you like to see in fantasy races. IE: Pointy ears, tails, fur, fangs, scales, human sized, tiny sized, giant sized, one eye, or three eyes. And/or whatever traits you like to see - such as mental, moral, cultural etc...