This is gonna be short and painless. But alas, its how I think things should be. Keep in mind that I'm talking about a fantasy MMO.
Items should be player driven:
The current popular formula is such that in order to get the best gear, you have to grind it out in a dungeon. That way, players will continue to play the game until they have the best gear. And when that almighty day finally comes, that five minute patch you just downloaded will shatter your dreams, because your item was just outshined by the new set of items in the new dungeon. Awesome. So assuming you don't commit suicide, you play on and work to get the new item. This frusturating spiral generates a (hopefully) life long interest in the game, and therefore produces monthly revenue to the company thats relieving you of 15 bucks a month. I've seen a game try to make the item market player based. Original SWG kinda did that. The best armor was crafted by expert craftsman who spent hours grinding to get the abilities to craft so well. I agree with that philosophy. Sure WoW has a crappy crafting genre, where you get components from high level areas and have a crafter make the weapon, but thats really trivial. I want a game where in order to get the best sword I have to travel halfway across the world and pay top dollar to a lifelong artisan who can make the best damn sword there is. And on top of that, the sword should only give me a slight advantage. Whats wrong with the way things work in real life? A proffesional swordsman could pwn a novice, regardless of equipment. Items should be vast and highly customizable, but mainly for flavor. You should be able to get a lighter blade, that adds a little speed, but it certainly isn't the 'purpose' of the game. Just a utility, the way items are supposed to be in the first place.
Guilds should determine PvP, nothing else:
Sure maybe a bold statement, but thats how I feel. I don't want to select 'good' or 'evil' upon startup. Of course, I am a pen and paper player, so I'm used to deciding that along the road. In an open PvP environment, which a popular blogger has outlined, it creates an environment in which everyone is on their toes. Certainly, there will be a-holes who raze noobies and laugh all the way. But in such a climate, alliances have to be formed to protect the weaker players. And the game should be realistic in that. 100 noobs should be able to destroy the top level player. Thats really how I think it should be. Of course, if a player is playing a high level character who is like a ninja, and uses tactics to take out a whole sling of 100 noobs, so be it, he kills them and should get their loot. But if 100 farmers were surrounding a knight, the knight would eventually be overran. Such a setting would make guild essential. The only way to be safe is to be with a large organization. Such organizations would have politics between eachother, and that would determine who you 'hated' and wanted to raze and kill. Not some pre-determined setting.
Real estate is essential:
I'm not sure if I'm alone on this one, but I am stubborn on it. I think a proper MMORPG should have real estate. It's not really somthing I can quantify, but its almost neccessity. Real estate should be destructable, repairable and purposeful. Think of it like an RTS's handle on buildings. Gaurd towers should give you and advantage in defense, though they can be destroyed. And repaired. Aside from the protection standpoint, it also allows for status. Who didn't want a huge nice house in UO? I think real estate should be emphasized and perfected. A system where you can buy and sell, as well as just 'take over' somones real estate. Another thing that will force create a player ran guild, and city even. Eventually, people would band together in such large groups it would create a kingdom, and maybe they vote for their leaders, or maybe their is a king. All could stem from a proper real estate system.
Minimum NPC interaction:
Ideally, though unrealistically, every single thing character should just be an avatar of a player. I am not sure how a developer could go about doing so, but I believe even quests should be given by a player for a player. In addition to adding a sense of realism, it would make for a more personable experiance. Instead of "Kill 50 sheep and bring me their wool for 2 copper" it should instead read "Hey, Celer, if you kill 50 sheep and bring me their wool, I'll give you a copper" "How about 2 copper, thats a little more reasonable" "Ok, deal.". Corny example, maybe, but its clear that NPCs take away from games.
Minimum Out of Character Protection:
Which I'll referr to here on out as OoCP. What I mean when I say OoCP is GMs. Yes, they are neccesary to fix bugs and exploits. I have no problem with accounts being banned for exploiting bugs, thats just lame, and ruins the feel of any game. But scams? I am 100% for a noobie giving up his stuff based on trickery, he gains experiance out of the encounter. There should be a system to address the problem, player ran cities should have bounty lists for outlaws. In game protection would be awesome, makes for a realistic encounter and also allows advanced players to outsmart the law. Obviously this is impossible with OoCP, so an actual theif in an MMO? Impossible. Theives in MMOs now are DPS. Some MMOs allow for lockpicking...of dungeons. Cool, I play a lockpick who saves his talents for unlocking hidden chests in cold basements protected by monsters. No, in fact that is not cool at all. Theives should be able to pickpocket other players. Other players should leave most of their gold locked in their rooms, but rooms should be able to be broken in to. Or, eventually, a smart enough player will use game utilities to set up a bank, a highly protected place for money. But even still, if you and a dozen friends plan right, you should be able to overrun a bank and amass the fortunes inside. Thats minimum OoCP.
One fricking huge server:
Yea, millions of players in one world is awesome, with limitless potential. I know its possible, EvE did it nicely and the game runs with stability (when I played at least).
Well, thank you for reading, I hope even if you disagree with some of my points you at least gained some insight as to what others are looking for in a game. I guess I would summarize by saying that I think an MMO should use every resource not just to make an engaging interface with quality gameplay and excellent character building, but they should also give players utilities to make the world a players world, not an NPCs world. That way, you would'nt have role playing servers, you would literally have to role play, if you talked smack you get killed.