Why is the game so popular?

It's aperture science, you wouldn't understand. WE do what WE must... because we can.

For the good of all of us...
... except the ones who are dead.

Science rage.

Because it's hard to NOT like it. It doesn't have a lot of the elements that turn some players off, like twitchy gameplay, excessive violence or gore, repetitive activities, etc. What it does offer is an amalgam of the best aspects of a lot of genres. It's a really good puzzle-adventure-shooter-platformer, immense in scale, and always full of surprises.

Portal 2 also kicks the immersion up to 11. It's not just a game you play through, you experience it. It's almost if someone made a game based on urban exploration, with the classic element of the evil computer out to get you. If you take your time, there are a million little details to delight in, especially if you dug into the story behind the first game.

Come ON! This is PORTAL. the best puzzle game out there. Addictive. Perfect difficulty. Lots of replay ability. Fun. Perfect.

==3

Because not all shooters require death and destruction. Of enemies.