A Clash in Civilization at kuro5hin.org while discussing Civilization democracy games - I won't go there, you shouldn't either - had this:

No matter how skilled you are Civilization, luck can still make or break your game. Luck acts in two ways; through the map, and through battles. Unless you use a custom designed map, the computer generates one randomly before each game based on a few user defined parameters such as size of continents and age of the planet. In an instructive demonstration of Jared Diamond's theory of geography determining history, the type of terrain that your civilization finds itself in at the start of a game hugely influences your future success; a civilization that starts in the middle of a sprawling jungle is unlikely to grow as quickly as one lying in fertile grasslands.