Survival, freedom, and success

A human's, and any animal's first instinct is to survive. It takes precedence over all else. After that is the need to be free rather than be a slave. Especially important is freedom to come and go where you want. Only after a man or woman can survive and be free, do they then need to be successful. This is the problem where MMOs always fail. When they are new, the game is exciting and meaningful because you are trying to survive. Even the weakest creatures outside the inn or other safe area can kill you. Then you need to be free to travel, to go to other villages or cities, meet with other players, explore new lands. This also is very meaningful and acquiring some levels, basic equipment gains you that freedom. After that, some feel the need to be successful, to go into the dungeons and kill the most powerful monsters. But not everybody feels the need to do this very strongly.
For an MMO to always be highly entertaining, a player's survival and freedom must always be threatened. At the very least, there should always be somewhere that a player cannot travel to safely. There is a large percentage of players who will never feel a strong need to conquer monsters in dungeons to gain more power, that will allow them better chance of conquering even more monsters. A player's basic needs must also be challenged constantly. It is perfectly acceptable for this challenge to increase in difficulty. Just because it is "outdoors" should not necessarily mean trivial. Just like new dungeon content should get harder and harder, so should outdoor content. Perhaps a new quest hub should require players to pair up, or in threes, just to get to a new flight path/quest hub. Perhaps faction work also would be necessary. Don't just challenge the overachiever dungeoneers. Challenge questers and explorers. Challenge everybody, in many different ways.