This is a difficult thing to answer, all communities wether it a gaming or any other will have idiots and good people.
With smaller fan based games, you will notice the good people more than bad, but with huge fan base like WoW you will notice more bad than good due to the size of the community.
Either way small or huge, the fan base has an equally proportional amount of bad and good anyway. Its like if it was a life design "Thou shall havest 30% bad people and 70% good people"
But.... It all depends on the developers also, if they are willing to sit and be a part of the community also and help people and generally converse then they will give a good feeling among a community.
Blizzard do the opposite in my opinion, the way they treat customers and give people little information on things going wrong is very bad.
So what has been the best community for me so far, has to be the Homeworld community, the modding etc was just fun to be within, nobody was badly treated and the developers were great.