They should be closed, either as subjective and argumentative or too localised. I would use the first if the answers are already becoming argumentative, the later if the question has no answers yet.
These questions open up a can of worms. It can quickly accelerate into a which is better flame-war, and as already been proven on SU, we do have the die hard Windows or Linux only crowd running around. It is not impossible to have a question like this have pure and honest answers, however it is a rarity.
I do however like the samples given by Ivo. A very specific question around what is needed to build a new computer and what to look for is definitely a good option. However a list of what specific hardware to get if not controlled can quickly get out of hand and will very quickly become outdated.
I will admit that this particular question seems to have remained civil, and I am therefore not going to close it myself. I will leave that decision up to the community, or if required, intervene if it does get out of hand and get flagged for moderator attention.