As a spinoff of my other Meta question:
In the case of a new question, which duplicates other, unanswered questions (or questions with no good or accepted answer), we should close the older questions as duplicates instead of the new question.
- The new question is more likely to attract new answerers, because a lot of us just trawl the "recent questions" feed.
- The new question asker is a lot more likely to accept an answer, completing the question, than the asker from a question that is years old (I've never seen a 2+ year old question accept an answer).
Therefore, if it's our goal to have good questions with good, accepted answers as a source of knowledge, it makes a lot more sense to close the old unanswered question than the new one.
Now, clearly "no good or accepted answer" is a judgement call, and it should be up to individual reviewers to make that call. But we can share this out as a pragma and start following it most of the time.