It depends what you are after, really. Personally it's down to Hera and Poseidon. Yes, some other gods have better myths, but when picking the 'best' god or goddess, I'd look at utility. Population Growth and Call of the Ocean are extremely important in rebuilding, and Earthquake and Sea Storm are pretty powerful as well. Kingly Gift is also the best value out of the resource spells. So if it comes down to spells, it would have to be Poseidon for me. If you bring in myths, it is a bit harder, as Hera has more accessible and easier-to-use myths than Poseidon does. But I do believe that Hera and Poseidon outclass the other deities when it comes to utility. Hades and Zeus are, in my opinion, the worst as utility tools as, although they have at least one great myth unit each, their spells are a lot more limited in usage and usefulness.