How bad of a king was George III?

Any answer to this question would be largely a matter of opinion, but there's no doubt that George III has earned the reputation of a bad king in the eyes of successive generations of historians, especially American ones. In relation to America, he tends to be portrayed as inflexible and out-of-touch, someone who saw the American colonies as nothing more than a giant cash cow to be milked for Great Britain's benefit.
On the other hand, one should recognize that ultimate political authority within the British constitutional system lay not with George but with Parliament, so even if the king had wanted to pursue a more generous policy with regards to the American colonists, he would not have been able to put it into effect.
If George can be criticized for anything, it's for placing too must trust in his ministers (such as Lord North) to find a way of accommodating the concerns of American colonists, people he regarded as his "children." All of the available evidence suggests that the king was keen to find some kind of compromise that would head off the prospect of a full-blown conflict. However, because his ministers couldn't or wouldn't hear of such moves, war became almost inevitable. When war finally did break out, George was deeply affected by the ensuing bloodshed, seeing it as something that could have and should have been avoided.