I see what you're getting at, and thank you for the Zelda analogy as that put it more in perspective as to what you were talking about. I was still thinking of it from a purely mmo standpoint.
No problem, I was happy to have the chance to explain it better. I get so caught up in the abstract mechanics sometimes and could probably save myself a lot of trouble with some concrete examples... it took me a minute to think of the Zelda example.
While I think Zelda or Metroid style barriers would be fun to add to MMOs you only play those games for 20-40 hours. Leveling is a big time sink in an MMO because you will often spend years playing one. What are you going to use as a progression metric after you've got your grapply swingy hooky freezy fiery infrared night vision goggles of d00m? Or are you just using equippables as an example? What would the non-leveling MMO player "collect" in order to access content?
Edit. Stoopid auto correct
Edited, May 20th 2013 7:51pm by LebargeX
Well, that's the definitive tradeoff of using levels. The main thing that they do for the developers (stretch out the game artificially) is the thing that most players don't like (adding excessive repetition). But they generally kind of work because some people are satisfied by the feeling that they're working towards something better. It stops working when the player realizes that there is nothing better... just more repetition.
Equippables are just an example, though it is possible (and pretty easy) to design infinitely horizontal equipment systems where the player can never have all of the equipment that they'd want to have--and you can definitely include abilities in that list. Many quests can be predicated upon the completion of earlier quests (that's pretty much a given in any narrative). Area access can also be used, though should generally be relied upon less often--reserved for special areas. Other gameplay features and UI, travel options, etc. are other possibilities.
Speaking very generally, you need players to fight their way through dangerous battles to reach their objectives. Large zones and lots of things to do in them. Getting from A to B is the challenge. Think about how much real estate is wasted in the average MMO today--the places that have no real purpose for you to be there. Now think of games like Zelda and Metroid. Was there ever a room or a screen that you DIDN'T need to go to? Not many. Were the monsters a credible threat for most of the game, or were they pointlessly weak after you had become strong enough? If the game is sufficiently difficult, players won't complete it too quickly.
And with a system like this, you can still do levels. But you might only do 5 or 10 levels. They can still serve the exact same functions if you really need to gate some content.
But ultimately the question shouldn't be, "How will we get players to keep playing without levels?". What we should ask is, "Why don't players want to kill our monsters? Why do we have to give them XP and levels to get them to do it?" In most cases, it's because they've failed to make the combat fun, so they're relying on the carrot to get you to do it.
Ok, now we're going to get slash fiction of Wint x Kachi somehere... rule 34 and all...
Never confuse your inference as the listener for an implication of the speaker.
Good games are subjective like good food is subjective. You're not going to seriously tell me that there's not a psychological basis for why pizza is great and lutefisk is revolting. The thing about subjectivity is that, as subjects go, humans actually have a great deal in common.