well,i've played so many MMOs its not even funny,
and what you and all MMOs need is,
lots of different quests and end content.
you know,no one likes straight grinding.
decent quests with moderate exp. rewards are something everyone likes.
and end content is key,when getting near the top levels,players find themselves bored with the lacks of things to do,since they are so high leveled.
also,player participation and events are great.
you know,small events,things that get the community together.
and lastly,GM participation,at least talk to players,even if you cant help them,people like it when GMs reply to them.
since you're actually here,and trying to learn what people want,thats a great start already.