Should we forget fusion and focus on geothermal power? Firstly I can say that I would love us to come up with a sustainable fusion solution.  However with the latest estimates being 2050 at the earliest for an effective fusion solution and the planets energy needs growing by the year should we not be looking at alternatives?
I understand that in the EU alone we are spending billions of Euro's on an experimental fusion reactor.
We sit on top of a thin crust which is in turn on top of a mantle with abundant heat.  Should we not be investing serious money into tapping into this heat source as a long term, sustainable solution to the planet's energy needs?
How far could we get if the money used for fusion was diverted to geothermal drilling and research?
 A: You can't directly compare investment in geothermal power and fusion because they're at completely different stages of development. We know how to use geothermal power; after all it's already used in many parts of the world. The problem is that unless you live conveniently near a volcano it's (currently) more expensive than using fossil fuels. Since the engineering issues are well understood, it's not obvious how more investment in research will make it significantly cheaper.
By contrast, no-one has managed to get a fusion reactor to produce more power than it consumes, or at least not for longer than a few moments, and no-one knows whether it will ever be commercially viable. But if it can be made to work its potential is vastly greater than geothermal energy. Unless we do the research we'll never know if fusion will work.
A: a) cost of ITER

Based on the European evaluation, we can estimate the cost of ITER construction for the seven Members at approximately EUR 13 billion, if built in Europe
ITER is financed by seven Members: China, the European Union (plus Switzerland, as a member of EURATOM), India, Japan, Korea, Russia and the United States. In all, 34 countries are sharing the cost of the ITER project.

So it is not the EU alone that is spending the millions.
Contrast the 13 billion euro to how much an aircraft carrier costs: the US by itself built 10 at a cost of 4.5 billion dollars each, total 45 billion..
So the expense of researching what will be practically a free energy machine of 13 billion shared by 34 countries should be put into perspective.
Now the cost of geothermal wells is documented, from a simple search one can have an order of magnitude estimate for the cost of single deep wells, down to 10km. Each well is about 10 to 20 million dollars. The 15 billion of ITER could drill order of magnitude 1000 wells.
That would not cover needs in gigawatts, imo, which are the world needs.

According to studies, an economically competitive geothermal power plant can cost as low as  $3400 per kilowatt installed

Geothermal is an interesting parallel source of power, where ever it can be extracted, but cannot beat fusion.
A: I don't think its time to scrap the whole idea, but definitely it is time to devote more resources to alternative approaches. Out of the top of my mind there are two non-mainstream approaches worth pursuing:
Focus fusion: or as some like to call it, 'spark-plug fusion' because its basically huge spark plugs generating strong magnetic fields during the corona discharge period, they also expect to minimise X ray emission by some clever manipulation of the magnetic field, but i don't get the fine details
Polywell fusion: this is another approach trying to keep a virtual electron anode in the center of a structure of geometrically aligned magnetic toroids that try to minimise the electron leakage rate by tweaking their circulation pattern around the toroids
A: If by fusion you mean hot fusion, the kind done in Tokamaks, then yes, we should forget it. This is a terrible waste of money--- the designs are not going to produce a power plant in 2050 or 2080 or 2100, or 3000, or anytime. It was a good idea, it just didn't pan out, and the scientists involved are constantly afraid of losing their funding, something which should have happened a long time ago. The major issue is that you don't get factors of 100 in efficiency from scaling up, so if the current billion-dollar projects do not produce usable levels of power already (and they don't), scaling them up is not going to produce a realistically competitive power source.
Different ideas for hot fusion, like inertial confinement, are promising. Although they are no closer to a power-plant today, they haven't been explored as well. The only scalable fusion we have today is the H-bomb. There once was a proposal for generating fusion energy by exploding hydrogen bombs in a gigantic underground enclosure. Even considering the enormous size of the enclosure, this would probably be cheaper and easier to make work than a Tokamak. Of course, the security danger of using hydrogen bombs in day-to-day activities probably rules this idea out.
Geothermal energy is very similar to extracting the heat from an underground nuclear explosion. It is a potentially limitless source of energy, and it will not require an open-ended neverending research program.
In this context, one must always mention the great work of Pons and Fleischmann on cold fusion, which is completely separate. This is a set of different research directions and ideas, and it makes all this hot fusion nonsense moot. It is clear from Pons and Fleischmann's seminal, era-defining work, that it is possible to use atomic scale chemistry to get fusion. This is where the hot fusion money should have been diverted back in 1989, and some speculate that the prospect of losing money led the hot-fusion scientists to suppress Pons and Fleischmann's work.
