In her 1979 article Gene-Juggling, Mary Midgley criticises Richard Dawkins' book The Selfish Gene with the words:
'Genes cannot be selfish or unselfish, any more than atoms can be jealous, elephants abstract or biscuits teleological.'
This seeming failure to understand what a metaphor is brings to mind the complaint by the robot from Frederik Pohl's 'Midas World':
'Ralph made that faint beeping sound that was the robot equivalent of a sigh: Human(ist*)s were so literal minded!'
*I mean those who study the humanities here, rather than anything to do with religion

But one can still ask whether the metaphor is appropriate. I would see the word 'selfish' as meaning more than just wanting to have the best that you can, it also implies doing so knowing that this will deprive others of what they want. Without this, if, say, there is plenty for everyone (or at least that is what you believe), then your behaviour can hardly be called selfish. It is the knowledge of what you are doing which is important.

One example given by Dawkins in one of his books (I'm not sure whether it was in fact The Selfish Gene), is that of baby birds crying out to be fed. If the parents respond by giving more food to the loudest cries then over time the species is likely to evolve so that the cries get louder and louder. Eventually they may become loud enough to attract the attention of predators, so that the parents will be forced to respond to them immediately. In a creature which was aware of what it was doing, this would be considered extremely selfish behaviour - but there is no reason to think that the chicks know what effect their cries have. But of course we are talking metaphorically, so we have to look for some metaphorical representation of this extreme selfishness. The trouble is.though, that there isn't any. On every level, the predator attracting cries are the same as 'hungry' cries, just louder. A switch which distinguishes between 'selfish' and 'unselfish' is nowhere to be found. It is the same when talking about genes, to be (metaphorically) selfish there would need to be, at some level, a distinction between firstly getting the best that you can and secondly, doing so knowing that this will harm others. I see no such distinction.
'The greedy gene'?
So should the book have been called 'The greedy gene'? It doesn't sound right, and maybe there is a reason for this. The OED gives another meaning of the word 'selfish' as ‘pertaining to or connected with oneself’, with no implication of greediness. Each of us has a 'self', which represents not just our consciousness, but the continuation of this consciousness over time. We automatically assume that other people around us have such a 'self', but we are also eager to ascribe selfhood to other beings and objects, regardless of their level of consciousness. This is why the Gaia idea is so popular, and tends to go beyond the original hypothesis that negative feedback tends to keep the biosphere stable. Although the idea that the Earth has some sort of mind would seem too far out, the idea that it has a 'self' seems much more appropriate. Looking at the various entities in biology - the species, the organism, the cell, the gene - it was Dawkins' insight that the gene could, at least metaphorically, be considered as having a 'self' 

Of course the title 'The Selfish Gene' doesn't indicate whether 'Selfish' is supposed to mean 'greedy' or 'pertaining to the self'. Maybe that's how it should be.