Oregon Trail taught me more about American history than textbooks ever did, likewise Age of Empires II than textbooks ever did concerning medieval history. One of those Carmen Sandiego games did a better job teaching me English than any textbooks or classes ever did.
And god damn RPG Maker (read: computer programming) taught me more about math than any textbooks or classes ever did. To say nothing of all the games that demanded I learn how to do complex arithmetic in my head on the spot.
Looking back, the core lesson I took away is that you need to find the subject matter fun or meaningful to be able to learn it. No amount of "effort" is going to help if you simply don't, or worse can't, give a damn about the subject matter or the way it's presented.