These days, when a company sets out to create a Massively Multiplayer Online Role-Playing Game, they don't so much of think of innovative new ideas. Rather they take other features from previous MMOs that players like, tweak them a little to either make them better or their own, and implement them. So naturally, to make the perfect MMO, it is only a case finding the best features to steal.
MMO design boils down to several categories that you need to fill, which include: story, character creation and customization, boss fights, quest design, loot , battle system, PvP, and crafting systems. Now it is only a matter of plucking the finest from the MMOs already out there.
Story - Guild War 2
This was a tough pick, it was split between Star Wars: The Old Republic and Guild Wars 2. In the end, Guild Wars 2 won out even thought the story utterly fizzles out at the end. Primarily Guild Wars 2 wins in terms of story because it doesn't really stop after your characters main story. There is still the living story to go through which ArenaNet adds to every two weeks. So thus, the lore of the world is constantly expanding.
Aside from constantly expanding lore, it is great to see an MMO where your character actually has a voice and uses it. None of that 'silently nodding in agreement' here. Your character has intelligent conversations and it is very immersive.
Character Creation and Customization - APB Online
I fell in love immediately with APB Online purely because of the customization options. You can tweak your character in every which way to make it look just perfect, it even allows for the aging of scars tissue to show how long your character has had it. APB allows for characters to design their own tattoos and clothing as well. Which, you just can't find anywhere else. Most every other MMO allows for just a few preset options, which cater to everyone's personal needs, but eventually you will run into a character that looks just like yourself. In APB Online, if you fully utilize every customization option on the creation screen, you will always be one of a kind.
For a while, Aion was considered for this role. It has some pretty in-depth customization as well, plus at any time you can go in and change your look and get a sex change.
Boss Fights - World of Warcraft
If you ask an MMO player what their favorite boss fight is, 80% of the time it will be a World of Warcraft boss. They have gotten a tad bit lazy with their boss encounters in recent years, but Lich King and before had some memorable and amazing boss battles.
Not only were they well designed bosses, but they were challenging. That is key, many MMOs dumb down their end game bosses so that everyone can experience them, however sometimes a little challenge is good for everyone. Where's that feeling of accomplishment if the end game boss is easy?
For example, C'Thun in AQ40 was near a masterpiece at the time. Banding together a massive group of 40 people to complete all the elaborate steps to beat him was an impressive feat.
Quest Design - Star Wars: The Old Republic
Questing in every MMO is almost exactly the same formula. Go here, kill this, collect these, and turn in. It's tedious, but there is no easier way to give out experience. After awhile, you stop even reading the text quest because it is just pointless and boring to do so.
However, Star Wars: The Old Republic spoils questers by giving a fully voiced game, even the quests. You rarely need to read and it is glorious to just sit back and listen. Instead of quests being horrible boring timesinks, they involve you in your character and add to their back stories.
Loot - World of Warcraft
There are a lot of bad things about World of Warcraft, but for a loot whore it is a paradise. There are literally thousands of different pieces of loot that can be won, gathered and crafted in Azeroth. Each piece usually being of a different and unique design, with the exception of some pieces in later expansions that are just remakes of older pieces.
Regardless, if you love beautifully designed weapons and armor, World of Warcraft is a good MMO to turn to just because of the sheer numbers of stuff. Plus, the stats on the gear are so swollen right now that at end game you will feel like a behemoth of ultimate power even if you are not.
Battle System - Final Fantasy XI
This was a difficult choice. Guild Wars 2 with their weapon-based combat system was interesting and the sheer number of moves in World of Warcraft made them both potentials. However with both WoW and GW2 you have move rotations. Rotating through the same thing over and over again until a boss is dead, it can get dreadfully tedious.
In Final Fantasy XI, the combat is more reactionary, you have time to think about what move is needed next rather than just button mashing the next spell in your rotation. Final Fantasy XI also encourages players to actually pay attention to combat as well with skill chains that can be achieved with other players. Unlike other MMOs, the lower level spells of XI don't lose usefulness either. They are still very powerful even at high levels.
PvP - Guild Wars 2
For most people who PvP in MMOs the most important aspect is that it is balanced. No one wants to pick a warrior class only to find out once fully leveled that the mage class is the overpowered way to go. However, balanced PvP is impossible to find and hard to achieve for most developers.
The pick for best PvP has to be Guild Wars 2, it can be imbalanced at times what with hard to kill Guardians and steam machines of murder that are Necromancers. However, you do not need to level a whole new character to be overpowered. You can just make a new one and once entered into PvP, you are max level.
Guild Wars 2 PvP is also not completely about killing other players, much of winning is merely being able to hold certain checkpoints to earn points. It's possible to have games where you don't have to fight anyone, just run from checkpoint to checkpoint backcapping.
Crafting System - Final Fantasy XIV: A Realm Reborn
Probably the best thing about Realm Reborn is that you can be everything on one character. You can be every battle class and every crafting class unlike other MMOs that limit you to a few. However, the reason that A Realm Reborn's crafting system sores above all others is that you actually feel like you are crafting something.
For example, in World of Warcraft, you gather all the materials then click a button and it gets made. In A Realm Reborn, you can simply craft the item or try to improve the quality for which you are rewarded with not only a better item but more experience. Sure it takes longer to craft a singular item, but the reward is bigger for your effort. Essentially they made crafting into a little mini-game.