In my experience, I would say it is just as effective as any other medium teachers use (books, movies, tv, comics, articles). I don't have clear evidence that it is the best way to teach, but it is definitely a way that should be taught. Every student learns differently and that one student who has been having a difficult time grasping a concept may finally understand after interacting with a game. These lessons have been some of my more fruitful lessons. They don't replace any of my traditional teaching methods, but they are a great addition/supplement to my course.