RIFT is up-selling what is typically bad news for a MMO company. Conan the Barbarian is now free to play. News we heard from Warhammer once due to server population declining. News we heard from DDO once due to lack of subscribers.
There is a wealth of theme park style MMORPG's on the market. Right now, I have 12 installed on my desktop, including WoW, LOTRO, DDO, Warhammer, and City of Heroes. All of these give us a fantastic world that we are only allowed to do what the developers designed for us to do. In City of Heroes/Villains, I cannot affect the world with my evil plots or save a blighted area and change it back. In World of Warcraft, I cannot make any meaningful progress in the battle for Alterac Valley, because despite how many times I kill that dwarf I just end up in the same battle 5 minutes later. This is how I define a themepark MMO, in case that was not obvious: the scenery is nice but don't touch it, you're only allowed on the rides.
Meanwhile, we have games like Terraria and Minecraft with a tremendous following. Though simplistic, these are polished experiences that people spend hours on just building and creating vast worlds. Search on Youtube for "Minecraft" and I guarantee you that some of the creations will amaze you.
Of course, it'd be easy for me to spend the rest of the post bemoaning how no big name developers are creating this experience. Which then brings us to Wurm Online. This is the experience I've described. Players can change the landscape, build houses and kingdoms, PvP against one another on a PvP server or join the PvE one and live peacefully. So...why isn't this game more popular with the kinds of crowds in Minecraft and Terraria?
Because theme park MMO's, for all we talk about them neglecting the world part of an MMORPG, give us a polished, streamlined experience that is enjoyable and does its best to cut out the bits that are unpleasant. You are a hero in an epic world who gets to take down dragons, not a simple peasant in a countryside chopping down trees to build a lean-to. You have to work to be epic, like in Eve Online. The people who run corporations built them from the ground up. Theme parks? Well, much like the new Harry Potter segment of the Universal Studios parks, you are a special hero who gets to hang out with the important people. That feeling of immediate importance in the world is satisfying, as much as we'd like to promote the wide wide world aspect.
So should theme park MMO's get the boot? No. they have their place. Sure, I wish there was more variety in the MMORPG genre, but I don't go to Eve Online to be an epic hero, and I don't go to WoW to be a peon.