There are many factors that are important to the game, however none come as important than balance, period. Regardless, to keep in line with your requested discussion, uniqueness comes second. Often times the games are simply far to familiar within the MC Code family.
Yet the third most important thing, in which this game lacks, is simply giving the users the ability to dis-associate themselves from having to compete against one another. There is simply to much focus with attacking other players, this unfortunately puts many new users in the immediate position of quitting before they actually get started. Sure there are mods in which supply limited controls, however, with the allowance of players being able to just increase their stats without leveling, seriously dimensions from the game balance. Giving the players the choice of competing against each other, well help retain newbies, as well as give them the opportunity to level up and raise their stats accordingly without the risk or forced interactivity with other players.
Just my thoughts,
Voice4Vision