MMOs are designed without a ‘game over’ screen, and one of the major appeals of the genre is that the player, rather than the game, determines when you are done. No matter how much you loved Final Fantasy 7, at the end you always kill Seph and the credits roll. In an MMO you can keep going, and ideally you should always have things you can do. Your character, and the world around him/her, will continue for you as long as you keep logging in.
That was how I saw MMOs when I played my first, Ultima Online, and that feeling of the game never ending still has major appeal to me. There was never a point in UO where I was ‘done’, where every goal was accomplished. I could always gain more wealth, or help my guild grow, or just get engaged in whatever everyone else was doing. UO was a sandbox MMO before the concept of sandbox was created. It was design to be a virtual world, a world that REACTS to the players rather than the players reacting to the game. When I finally moved on from UO, it was not because I had killed the final boss and the game told me it was over, but rather it was because I was done with my character, I had accomplished what I wanted.
It’s 2009 now, and while the MMO genre has exploded in popularity, we have very few sandbox MMOs. EQ1, and to a much larger extend WoW, popularized the theme park MMO, with one of the more basic differences being that the game more or less dictates your actions (sets a path), rather than reacting to whatever the player is doing. The advantage of this is that every player always has a goal, and more importantly always has a carrot within clear sight to keep them going. A well designed theme park MMO will always guide the player and keep them on-rails, removing the chance they may stray or get lost, or even worst, find themselves without a goal or motivation to log in.
The genre’s current top sandbox MMO is EVE, and the number one complaint about it is a lack of direction. Players hear all about the endless possibilities and the exciting things happening, yet when they go to log in and experience it for themselves, they more often than not are unable to find what they are looking for. Or they find the path only to learn of the barriers in front of them before they reach whatever goal attracted them. (Letting off a Titan shot sounds awesome, but actually being able to fly a Titan is far beyond most gamers limits)
The original appeal of MMOs, an unending world with limitless choices, is also the genre’s biggest crutch when it comes to appeal to the mainstream. EVE may be the genre’s best designed, best looking, and most advanced MMO, but unless it adds NPCs with golden icons above their heads, it will always remain a niche product. (Which is not to say its not a success, because it is)
The major problem with a theme park is that eventually you have been on all the rides, and while repeating the best ones is fine for a time, even that beings to grow tiring. Adding more rides is possible, but customers will always ride then to boredom faster than they can be built, and if you are sticking with your theme, each ride gets boring faster than the one before it. Change the theme and you might alienate a portion of your customer base, driving them away permanently (in the theme park world, this is called Not Good Entertainment)
This is why I’ll always favor the MMO going more towards a sandbox design over that of a theme park. I know that no matter how fun a theme park may be, it’s time is limited, and eventually my character will be forced to retire earlier than I had planned. While no actual credits will roll, the cap will be hit and the gameplay will change. At the same time, I’ve seen enough MMOs to know that designing a good sandbox MMO is very difficulty, and even the best laid plans go up in smoke the day the players are let loose in the world. In that regard, the theme park is the ‘safe’ bet, an almost guaranteed quantity of entertainment, while the sandbox will always remain hit or miss. The misses may sting with disappointment (hi Shadowbane), but the hits more than make up for it.