There are many things that can make a good administrator. The following are:
1. Can be on at least twice a day. Being active is crucial, especially if you are the only admin. If you cannot get on twice a day, you might want to suggest appointing another admin to fill in when you are not there.
2. Can take the role of a Sage, and not a Dictator. The dictionary definition of a Sage is: "A person full of wisdom and prudence." As for dictator, we should all know what that is. Basically, you want at least one active administrator that knows how to run a wiki, knows how to make it successful, and that type of stuff. However, as mentioned by several people, administrator rights are not a form of power, but rather just a person who has access to all of the housekeeping stuff for the benefit of the wiki.
3. In some cases, making your wiki a republic for the editors there is crucial. The definition of Republic is: "A state of government that puts power and structure in the states' interests (hence the term Republican)". What does that mean? Basically, if you put the structure of the wiki in a way that feels fitting for the majority of the people. For example, if the wiki has a group of chatty editors, a chat room might not be a bad idea to put up (however, know when any feature is being misused). Another example is this: some wikis enable the "Comments" feature to make comments look like they are on a forum thread. Yet, you may not even need a single feature if the editors do not really care for them. Be sure to have a type of republic that is fitting for the majority of the editors on the wiki. (P.S. I still think the Top 10 lists feature is redundant, because you can create one manually.)
4. Be sure to give off a good impression as an admin to other users. Alright, this is principle number two to editing, number one being, "Respect yourself, and respect the other editors." You do not want to come off as abusive, yet you do not want to be too forgiving to vandals, because most of the time, vandals could not care less about being blocked.
This is a basic outline of a good administrator. I might have missed some things, but these 4 points are good to follow.