Eco

Despite a brief tutorial on basic survival, the game has such a large (and still growing) amount of game mechanics, meta layers and complexity, that it takes good 20-40 hours to just grasp the core principles.

A fun game where you do actually need to cooperate (unless you purposefully look for a low co-op server or play offline alone) Something you can play for just a bit when you got the time and watch stuff grow over the course of about a month (typically).

Played multiplayer and I don't know how, but they've managed to recreate the old feeling of WoW in this game.

It has decent graphics, there's a ton of stuff to do and you can build whatever you come up with (as long as you keep an eye on not destroying the enviroment too much).

This game asks quite a lot of its players (in terms of learning curve, consistency, attention), and if you're in a position to fulfill these, it's great.