IMO it needs to be simple and clean, easy to identify both close up and far away. As someone mentioned, the most excellent recent Indian head logo was great, but did get a little busy if you were far away or if it was small.
I like simple and clean logos. Some examples of excellent ones are the MN Vikings, Cowboys, Detroit Lions, Packers, Colts, etc. Some that I think are bad are the Jaguars, Broncos, etc.