I don't think a "good god" is a coherent concept. I think to have god-like power, evil is implied, simply because that god had to ... appear as part of some process, and that process requires contesting power in some real way. And in that contest, one can be good and express goodness, which means not doing evil( a limitation) but evil does not share this limitation. Evil can appear to do good in a perfectly convincing way( that's a function of evil), However, good can't do evil in a convincing way-- it's limited in that sense. Therefore, evil is more powerful than good, and if we're talking power(gods), they can only be evil. The same is true for power in general, here on Earth. The most powerful thing that exists on Earth today, appears to be deeply evil in nature in a way that cannot be defeated by something good.