I feel there is a discrepancy between games used for recreation and games used for education. Educational games usually have poor graphics and few interactions although modern games have great visuals and mechanics to engage people. I haven’t known one appealing educational game that can let people spend 40 hours or so. (but it’s also very possible that I haven’t seen them. ) The reason why this happened is probably as Prof. Pursel said in class, educational games do not generate profits. Another key thing is the accuracy. There are a lot of games that feature historic components, but they are processed or tailored history, and the character design and architecture design are borrowed from another time period. On the other hand, people tend to think games as they are not something that you can learn from. But this is not the truth.
However, I can easily see how games can greatly help people in studying of different subjects (and make studying less painful), if government funding or industry investments have developed. In history class, for example, instead of showing students a documentary or a movie, games can be introduced to let students play through a history. This way, they are not exposed to fragmented information from the past. They learn events together with the architecture of the time period, the common people, the royal life, the music, etc. Think of this happening in VR, future VR: you walk in a dark, gloomy street in Paris with wet clothes clingy to your body, in a crowd of people, walking towards Place de la Révolution to see the execution of Louis XVI (Well, this might not happen in middle school, but something immersive like this.) You listen to them talking, why or why not they want the former king dead, to get the understanding of French revolution. Also, more what-if questions can be asked, like what if the Axis powers wins WWII.（The Man In The High Castle）
Virtual lab is also possible. In botany class students are not looking at the pictures of trees , leaves, stems, etc. They are put to the virtual forest where they look at the tree species and identify it.
Even in the fields that visualization and immersiveness are not so important conventionally, games and VR are potentially useful to understand concepts that are non-existent in the Earth. These are two articles about visualizing non-euclidean surfaces in VR: this and this. And in physics class as well, such as what happens in a planet with different physics laws or parameters.
