I think if there was one game you could single out as the best computer game ever, it would be Minecraft. Out of the box, there are several ways to play it: creative mode where you cannot die and have all the resources you need to build whatever you can imagine, and survival where you need to mine and gather your resources before you can build anything and at night monsters come out to kill you. Then in survival you can just keep collecting resources and build whatever you can imagine, or you can try to finish the game by killing the Ender Dragon, which involves travelling to two different worlds and surviving some pretty tough challenges. Speedrunners can do it in 20 minutes, I cannot do it at all.

Then there is a whole community of online servers which can run a variety of plugins that completely change the game, from a wide variety of minigames that may not involve any mining or crafting at all, to a game where you're resource-starved on a floating island, to a game where the resources available are totally different.

I rarely play it, but I can totally see why my son, nephew and all their friends are addicted.