I'd change very little about Civilization 4 -- even five years after the game's release. But don't mistake that for a lack of desire for Civilization 5; I'm salivating at the prospect of spending more nights conquering the world with my super-cultured, democratic, Jewish Vikings.
I have a few ideas about aspects of the game that Firaxis and Sid Meier can touch up, and I'm going to list them here for your reading pleasure.
Civilization V continues to be one of the most popular grand-strategy games you can play on Steam, for about three years.
Love strategy but your processor and graphics card doesn't love you? The best strategy games for low-end PCs have you covered.
Philip Boyes:
When I was a kid, I played a lot of Civilization 2. I played a lot of strategy games in general, but having a deep love of both history and sci-fi, the epic sweep of Civ 2 from prehistory to the stars held a particular appeal. I loved taking my little people from their huts and ziggurats to the world of science and advanced space-flight.
Totally agree about the diplomacy. The AI players seemed pretty irrational at times and the whole diplomacy felt very all or nothing. They tried to quantify things in Civ IV by scoring based on religion, tension, trade, etc, but it never felt like it mattered all that much. Maybe having land disputes (instead of always having clear boundaries having things more realistic with different groups/nations both trying to claim the same parcel of land).