Which are the points on Earth that receive the least solar radiation on average?
On an average those would be the poles. As you correctly pointed out, due to the tilt of the Earth's axis, there are large areas that receive very little and sometimes no sunlight at all and those change throughout the year. But on an average, poles are the ones that get the least amount of solar radiation.

For example, see this paper and in particular have a look at figures 2.6 and 2.7. The last of the two figures, which I will link here shows the graph of annual mean insolation as a function of latitude.

 

Here it's obvious that poles do receive the least amount of radiation on an average. But this is the idealized case, i.e. insolation at the top of atmosphere. 

On the other hand, if you do take prevailing atmospheric conditions into account then it's a competition between the area between Spitzbergen and Iceland in the North and areas just off the coast of Antarctica in the South. Taken from Wikipedia article on Solar Irradiance the top picture shows top of the atmosphere insolation and the bottom one - ground-level insolation.