I've played Oregon Trail. It's a good game, don't get me wrong, but when it comes to an educational focus, I always found those three games to be absolutely awesome. They taught me as a kid (well, Zoombinis was when I was 15 so it didn't teach me so much), while Oregon Trail just didn't feel like it taught me anything. Bloody fun to play, though. If I were to consider Oregon Trail an educational game, I would probably also consider Civilization an educational game (and SimCity, and Flight Simulator, and Dwarf Fortress, and that one Noah and if you really want to push 'educational' to wider audiences then there's also the Noah and the Ark version of Wolfenstein 3D they once made xD). They teach me about how to play the games but I don't feel a huge amount of education coming out of them. Perhaps I'm focusing more on "in your face" games.

Also, I hope you're not suggesting that those three games I mentioned aren't some of the best games to have ever been made.