Games still have great potential to educate, just not in the ways that many educators expect. While designers should still be careful not to include anything factually incorrect, the value of an interactive experience is the interplay of simple concepts, not the inclusion of numerous facts and figures. Many remember that the world’s earliest civilizations sprang up along river valleys - the Nile, the Tigris/Euphrates, the Indus - but nothing gets that concept across as effectively as a few simple rules in Civilization governing which tiles produce the most food during the early stages of agriculture.
I see this all the time in educational games. The focus is on the content, not the game or the game mechanics. A great educational game should be an experience you enjoyed, but you walk away with knowledge and understanding. The content is secondary to the experience, but interacting with the experience rewards embedding the content.
I've been a big fan of incidental learning and believe that to be the key to the success of games like Mathletics.