For what it's worth here's what I'd like
Diplomacy
1. Remove the erm... humorous tone to diplomacy, on first contact you should be greeted in a way that that particular leader would greet someone, perhaps having humorous diplomacy could be turned on in the options menu...
2. On that same note make the images of leaders more realistic looking, I don't really like the cartoonish look of some of the leaderheads.
3. I agree with having terms for a peace treaty IE War guilt (Relations hit with all nations) reparations (X gold to winner per turn for X turns)
4. Ability to "red out" items on your side of the diplomacy screen so as to avoid constant nagging by Monty to go to war.
Economy
1. Deficit spending so long as you are on good terms with another nation you should be able to borrow money from them. This will of course require some changes in how money works
2. Exchange rate, more or less a pipe dream but I'd like to see an exchange rate, the more bullion you have the more your paper currency is worth and vice versa, this will effect trade and happniess and the usefulness of economic improvements
3. Economic stats: Prosperity, Bull Market, Neutral, Recessions, and Depressions should be included depending on how you are fairing economically
General
4. I'd like to see the value of a resource be detirmined by supply and demand, for instance if everyone has sugar sugar isn't worth much in a trade, but if no one has gems gems are worth a lot. The same should go for
generated by luxuries.
Aesthetic
1. Flavored units: If your an African Civ your Marines and Infantry shouldn't all look like Srgt. Emery.
2. Bring back the palace.
Map:
1. Improve rivers vastly, ships should be able to travel across larger ones. If multiple civs are built along the same river conflict should arise if people upstream are polluting or building a dam.
2. Terrain height should defiantly be a part of the game.
3. More natural features, salt water lakes, caverns, waterfalls etc.
4. Strategic points: Moutain passes, river fords etc. Terrain can be a great weapon in times of war, just ask William Wallace, Leonidas, Sun Tzu...
Government:
1. More civics, the civics in Civ IV were too general. I think they should expand the new constitution system from Civ Col. In addition each civic needs to have good and bad traits. Each civic option should have 2 or more sub options. (IE Representation by population or all representation is equal, enslavement of a certain group, or through judicial means. A one party, two party, or multi-party system?) that have their own consequences.
2. Building off that there should be a complex senate, unhappy citizens vote in senators from your party's opposition who will vote down your wars and make peace without your consent. If you don't like it then you can change to another civic.
UN/AP
1. Allow members to leave/be expelled/refuse to join.
2. Make votes trade items (IE Oil for voting no on World wide Free Religion)All
3. Allow a second UN to be built to oppose the first one.
General:
1. "Cancer clusters" instead of global warming as a result of nukes.
Thats all I can come up with right now rest assured I'll have more..