Well let's see.
Virtue is basically a category. A word describing a list of good traits ahuman can or should have. For that list is not just a list of possible traits in general, it's specifically a list of good traits, traits to be aspired. There are a lot of virutes (in fact alone in the example part of the wikipedia article there are over a hundred examples of traits seen as virtues). Now of course it differs. What i see as virtue another might not and what another sees as virtue i might even see as harmful. But in general i would say i have good associations upon hearing the word virtue. (Mostly for i have my own virtues, i mean i don't have a concrete list lying around herer where i put them down, but if asked i think i could list quite a few things i would see as virtues, as good character traits. Of course only in my opinion.)
Duty. Hm. It's a bit more complicated with this one. I think it often is named a virtue, but i'm not so sure. I don't think it is necessarily bad, but i wonder wether it is really 'good' if someone does something just because it's their duty, because someone (or themselves) command them to. I think it would be better if people do the things because they think they are important or it is the right thing to do. Also, as Anthile mentioned, i think this is something that most easily can be abused, by both sides really. Just think of all the War-stories where soldiers just "fulfilled their duty" etc..
Citizenship. A good thing, as it means that the citizen has at least some say in the society he/she lives in (as you could see in walfins post). Although it also is not separable from 'society' and i have some problems with that in general, but that's another topic.
Responsibility, Loyalty... Those are virtues. I don't like to take responsibility, because i know i'll take it seriously and it is something tiring (yet of course important), but if i must (or noone else would in an important situation) then i do my best to fulfil it. (At least i hope i do/try to do). Loyalty is something i do feel, towards my family and friends too (although i don't have much of those, i mean real, close friends). For example it means that despite me not agreeing with my parents' choice of lifestyle (not with everything at least) i do still support them in it. That certainly ties in with my general attitude, specifically the fact that i always try to help people who need assistance, but it goes further with my family (meaning i do more for them than i would do for foreigners).
Of course Loyalty is another of those virtues that can be abused from those who you feel loyal to.
In general i would say, Virtues are traits that have to come frmo the inside, or at least while being shown to a person from the outside, have to be processed and finally out of inner values and conviction found as worthy. I don't think they work when just enforced from the outside. Oftentimes though those lists of virtues are stated from some authority be it mundane or religious/spirtual and meant to have better followers. And while i think the general idea of Paladin is a good one the depiction of Paladins in most fiction i saw/read so far is rather that of an obedient Officer/Knight who also adheres to other virtues, but almost always in the list of his virtues there is Obedience/Duty towards his King/Chief of his order etc. Also those Paladins are depicted as very strict rule- and law-abiders. Imo a better Paladin would be one who is the virtue-driven defender without any King or Chief/Order and whose list of Virtues he adheres to does not contain "Duty".
(You might see my usertitle that is "Paladin of Patience" at the moment, i feel driven to explain that ith Paladin i mean the latter sort, that i just explained. The sort of Defender of the Weak that does that by his own inner virtues and values)
(Also, all "he" above can of course be "she" too
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Ogion