Portal 2 is one of the very few games which I remember the most due to its captivating storyline. It also brought the plot of the original Portal game into the next level, considering how much you learn about Aperture’s history in this sequel. One moment that I remembered the most from this game was being introduced to the massive spheres deep within the Aperture underground which contain the forgotten parts of Aperture’s past. The attention to detail of how the different eras look is amazing.
The game also has a co-op campaign, which I’ve never really played much since I have no other friends to play with. Sad.