There are many different types of Geothermal Energy. If you want to do an appropriate comparison of technologies, the three should be concidered by how much "electric" they can generate. Also, Solar Panels can create heat or electric. For this analysis, lets just concider the electric generated. Of the technologies you mentioned, geothermal (Hot Dry Rock) generates the most energy most economically. It can create 1000 kW (kilo-Watts) for approximately $40. See the attached page for a graphical comparison. The chart conciders the type of generation by cost of equipment, efficiency of generation, and cost of fuel (for the fossil fuels comparison).