I love the civilization series, namely Civ 2 and 4. I've found that it not only is quite fun, but teaches alot about history, and how the world works. While the gameplay is not accurate, elements of the game are based on real world events, people, places, and the like. Also, the game provides excellent background on the real life counterparts of each part of the game.
Sid Mayer's Civilization is the game series that I play them all. This is briliant game from first edition. Original thematic and extremly playible scenario. I think Sid Mayer is the best game maker ever...
I've played 2 and four. Four doesn't run too well one my computer though.
I liked 2, didn't like 3 very well, and am still waiting for the 4th one to drop in price before I purchase it. I don't believe it will run on my current machine, so I might have to upgrade my machine to even play it.
Sid Meier is a pretty good game designer, but I don't know if I would say he is the best ever.