I'm sorry that you can't find a game though.
I am sure that my suggestion of the The Sims isn't going to fly, but I was wracking my brain trying to come up with something.
It's sad that MYST is ending and it might take you a while to get over it, but I am fairly sure you're not going to find another game that will "replace" it. It was one of a kind and now it's gone. You'll just have to try to find something completely different to do that's still fun in it's own way.
You could have a gander towards this website:
http://www.mmorpglist.com/
They claim to be a list of every online game. Of course a lot of these are going to be really bad, but you might see something. They have them broken up by category and I saw they had a "real life" section.
