Critics are not game-literate, so they can't appreciate them. They know nothing about mechanics like strategic imbalance, the Skinner box, achievements, power creep and other concepts I myself am only becoming familiar with thanks to the thoughtful folks at ExtraCredits[2]. They don't know anything about how video games tell stories, challenge players with moral choices, or the brilliant innovations artists have had to come up with to work around hardware limitations in both graphics and music over the decades. If you aren't literate in gaming, then of course you can't appreciate the many many layers of artistic expression from algorithms to writing to graphics to music and mechanics that go into making a game.
Video games are more profitable than films now. Critical theory surrounding video games simply needs to rise to the level of other mediums before more people will respect it. Remember, films were originally considered such a waste of time no one bothered to preserve 75% of silent films[3]. As the new generation of game-literate kids grow up, I trust that games will get the respect they deserve.
[1] http://journals.sagepub.com/doi/abs/10.2304/elea.2007.4.3.29...