Yes, voters and elections can do a good job at electing judges. For years people have been attending elections and voting for who they want to see in office, whether it is for president, city councilmen, etc. This also includes judges, so I see no reason why voters would not be good at electing judges. However, one could argue that it is a matter of opinion; one person could think the people are great at elections simply because the person they want wins while another person can say we are awful at it because the worst person always wins. But when it comes down to whether or not our process of voting and election is successful and efficient at appointing a new judge I think the obvious answer is yes. It works and we continue to do it the same way.
The United States is a democracy for and by the people. We, the people, are responsible for choosing our leaders. To allow us to pick our legislative representatives and not afford us same power over the judicial branch amounts to tyranny. The people could most certainly pick more unbiased judges than political entities.
The problem with holding elections for judges is that it is impossible to predict the judge's position on most cases. The judge might be a conservative person, or a liberal person, but the type of sentence he or she is likely to issue is usually evident only after the judge takes office.