Let's start with the basics!

What is Minecraft?
Minecraft is and indie, sandbox game, almost everything in it is made out of blocks, squares. It also has a randomly generated open world that's almost infinite.
When did it get created?
2009
Who created it?
Notch, a game developer, Minecraft would have been a small project that was based of other older games.

How can a game be popular through years, not only when it comes out?
The answer isn't  as complicated as some people may think.
How do you play a linear game, that has one story, maybe some downloadable content, nothing else?

You play through it once or twice, maybe more times if it's really good. But it has no change, you do the same thing over and over and over again.

What do you do in a sandbox game?

Play it multiple ways, do multiple things and you mostly can not finish it. This is why sandbox games are "alive" for a longer time, because they offer more playtime.

As we know, many people don't have strong computers, that's why indie games with "low" graphics are popular.

What else makes you spend a lot of time on a game?

Multiplayer and a big community, Minecraft's community makes lots of different things for users to play, from servers with minigames to maps with complicated technics behind them. (Let's not even mention mods...)

What does Minecraft give?

1. Almost infinite capabilities.
2. Active, creative community.
3. different multiplayer modes.
4. Easy to play even on bad computers.

This is what made it so popular, the community, you, yes you in front of that screen, every time you make a blog, a map, a texture pack or a mod, remember this! You are keeping the game alive, you and the other players are what made Minecraft what it is right now!