Which duplicate questions should be closed? [duplicate]

Question

When a question (probably with several answers) that was asked a long time ago gets bumped via an edit or another answer sometimes it is discovered that there are duplicate questions. In most cases the questions get closed very rapidly.

Take, for instance this question: https://stackoverflow.com/questions/5132943 which was asked on Feb 27 2011. Yes, it did have duplicates which were pointed out within 5 minutes of asking. The question was not closed until today (Dec 20 2012) when someone bumped it.

Looking through the related/duplicate questions posted as comments to the question, I found that most of them are not closed.

My questions are, if all these other questions have been detected as duplicates then which of the questions should be closed?

a. Those that were asked at a later date?
b. The one with fewer answers?
c. The one which was just bumped?
d. Some other criteria?

Answer 1

Simple. The best question with the best answers is the one that should be kept open. Even if it is newer or generated less votes.

The question with the best answer, which gives the best solution which is applicible for the widest array of cases is the one that should remain open.

Some Examples.

Answer 2

I think sometimes we might tend to forgot that a big part of the idea behind Stackoverflow is to create a repository of high quality questions and answers to be used (for the future). Much of the sites features are based around this idea, such as the fact that (almost) anyone can edit anything.

As such I would say that the goal is that the best answer should remain open regardless of which question was actually posted first.