MMOs, or Massively Multiplayer Online games, have a long history, but most of that is the ubiquitous "MMORPG", from Everquest to World of Warcraft. MMORPGs have always been the dominant form of MMO, but recently there has been a push towards other kinds of MMOs, especially MMOFPS like Planetside 2 and Firefall. In this article I'll discuss why MMORPGs are so popular, some of the issues with the way they're constructed, and why I think games like Planetside 2 more naturally use the MMO concept.
Whenever you make a game, including an MMO, you should consider how all the elements work together. When making an MMO, you have to think about WHY your game is an MMO. I think that if it's constructed properly, playing an MMO 'solo' should be a significantly inferior experience, which often isn't the case for games like WoW and The Old Republic. These are games where the main questing is actually balanced towards solo play. I don't know about you, but that seems pretty counter-intuitive to me.
The MMO part of the game and the rest of it should work together to make the full experience. Consider Planetside 2, where you basically have a MMO version of Battlefield - the game is persistent, with consistent character progression, on a massive MMO-sized map with up to two thousand people on a single map, and up to hundreds in a single fight. The multiplayer parts and the shooting parts mesh together to form a single, cohesive game.
MMORPGs don't do this meshing of design particularly well. You have the RPG parts, where you go questing, kill monsters,and level up and otherwise progress your character, and then you have the "MMO" parts - things like warzones and raids. The end result is that you have two very different experiences in many MMOs, the 'leveling' phase and the 'endgame' (You might add 'PvP' to that list of experiences, depending on the game). The sharp divide between these phases is almost certain to lose a lot of people who were fans of the leveling phase - this is The Old Republic's major failure, in my opinion. I personally much prefer the story/questing phase of the Old Republic to WoW, but from most accounts the endgame and PvP are.. lackluster at best.
The reason these "WoW-clones" are so common is much the same reason modern military shooters are so popular - a follow the leader process. World of Warcraft is a massive cash cow, with 12 million subs at peak and STILL more than 10 million (technically it dipped below 10 mil but it's back above with Cataclysm), and publishers and developers think that if they essentially copy the WoW model but make a few changes, they might be able to get a piece of the pie - but just like with Call of Duty in the shooter market, it hasn't really worked for most. Just like with Call of Duty, after the initial breakthrough, WoW is self-perpetuating - so many people play WoW because so many other people play WoW. It takes something significantly different to get a significant piece of that WoW pie, and that's why games like GW2 tend to emphasize how they are different. Guild Wars 2's dynamic events are a good example of a feature in an otherwise very WoW-like game that use the nature of an MMO in an intelligent manner.
The industry seems to be slowly realizing that making WoW clones isn't the best way to make money. More and more we hear less of 'WoW clones' and more of 'WoW killers' - MMORPGs that are supposed to be BETTER than WoW in fundamental ways, like GW2's world dynamism and SWTOR's emphasis on story and voice acting. There's also been more and more studios experimenting with the MMO concept, implementing it more naturally into the game. Even the line between MMO and just a multiplayer game blurs with games like League of Legends and even some shooters - games that still have 'matches' and no persistent play between them. (I'd consider a game to be an MMO if it doesn't have a single player offline component, although most online shooters like Blacklight: Retribution aren't generally considered MMOs)
Personally, an MMORPG seems like a contradiction to me, although that depends on your definition of RPG (Which I'll talk about in another article.) An RPG should be about roleplaying, IMO, and I've yet to see a system that convincingly allows multiplayer roleplaying. Most roleplaying is done out of the given mechanics. Ironically, the best MMOs for roleplaying are actually not MMORPGs - they're games like EVE, where player and character motivations are essentially the same, and the roleplaying comes naturally from the mechanics. Think about it: MMORPGs are all about raids and PvP, and these are all things that are dominated by player points of view - mostly grinding for equipment or points of some kind. Even in The Old Republic, roleplaying is mostly limited to player character interaction with NPCs, not interaction with each other. It's essentially a single-player experience with MMO conventions like guilds and raids taped on to it. Contrast this to EVE, where you hear about corporate plots years in the making, or to a shooter where you have people calling for fire support or commanding a squad - all, essentially, in-character without any conscious effort to 'roleplay'.
All of the elements of a game should work together to form the whole. MMORPGs don't do this particularly well, due to the way they are constructed. I'm not saying that it's impossible to make a natural feeling MMORPG, just that in my opinion the WoW model isn't the way to do it. That doesn't mean they aren't enjoyable, either, but I think it's pretty much indisputable that they could definitely flow better than they do now, and developers are beginning to realize that and experiment with the current dominant model.