As with all technology, there needs to be moderation. Take breaks between games. After playing 30 minutes, give your eyes, hands, and mind a break. You can read a book, play outside, draw a picture, create art work, or write a story. You can come back to play your game later that day or the next day.
Also keep in mind that the options of educational games have increased.
For a list of free educational apps, please go to: http://kingswoodes.wcpss.net/apps.html
For a list of online educational games, please visit: http://kingswoodes.wcpss.net/students.html