Okay, everyone, I need your attention!!!
Starting tomorow, I will not be near a computer for a week, so I want you all to put your top ten or so favorite changes or additions for civ 5 in one post, so that I can put your ideas in faster when I get back.
OK, in summary:
1. Bring back separate attack and defence strengths as in Civ 3, and firepower and hit points as in Civ 2, and scrap the rock-paper-scissors model of who is strongest against whom. Scrap unit promotions.
2. Scrap civics and bring back fixed governments, about a dozen or so, with capabilities upgrading significantly so you essentially have to change government several times during the game to keep up.
3. Have about four hundred techs in total, most of which (>90%) are not optional, split over at least seven distinct Ages (ancient, classical, medieval, renaissance, industrial, modern, space age, optional future ages). Increase the number of units and wonders appropriately, allow production to shift freely between them, and make the wonders worth something, like in Civ 2/3, rather than nerfed as in Civ 4. Average unit strengths should at least double over the course of any age, so that more advanced units are exponentially more likely to defeat earlier ones.
4. Have air units be real units, as in Civ 1/2; have sea units be capable of attacking land units as in Civ 2. Have more stealth units, more "soft" units (missionary, corporate executive) and upgradeable caravan-type, diplomat-type, spy-type, worker-type and settler-type units. Have settlers and workers cost population points rather than stalling growth.
5. Scrap the culture slider; have culture be purely a function of what you build. Allow culture to convert enemy cities. Have a cumulative chance that any enemy unit on your territory will be converted by your culture. Change the culture win condition to converting the entire planet to your culture.
6. Have finite resources, which contain a fixed amount of productivity. Allow some of them to become more productive with increased tech. Have trading any resource require building a caravan and getting it to its destination.
7. Bring back corruption (with multiple Forbidden Palace-type small wonders becoming available over time), pollution, unhappy citizens and civil disorder and the +50% bonus for railroads.
8. Allow multiple "layers" of terrain improvement (irrigation/farming with chemical pesticides/GM crops, second and third layers of mining with gunpowder/robotics, road/railroad/high-speed rail) and other forms of improvement (bridges across straits; coastal sea conversion to polders; sea square modification with workers on boats, rather than one-use work boats; late-game terraforming of any kind of terrain.) There should be
no unusable squares.
9. Scrap unique units, buildings, and leader traits. Have the "traits" of a civilisation arise dynamically from the player's strategic choices; empower numerous different strategic choices as equally valid ways to win. Keep civilisations distinct by personality, strategy, and preferred choices, not by look-and-feel. The graphics need to tell you what a unit is, whose it is, how healthy it is, and what it is doing. If they succeed at doing that they can look like Civ 1.
10. Optional underwater and more detailed space exploration/colonisation options should be made available with optional future ages, working as distinct maps a la Civ2:ToT.
In summary: There are any number of empire management games out there. What makes Civ Civ is that the empire arises as an emergent property of the cities and all the smaller-scale decisions involved. Do not weaken this by forcing the player to use larger-scale coarser tools or blocking them from fine-detail optimisation of every detail of their empire. Yes, I do mean "more micromanagement", at least as an available option.
(Oh, and have a big sign come up every time you start the game saying "This is a game. Approximations have been made for the sake of gameplay. If you have problems with the realism of these approximations, they're your problem; please do not whine about them on CivFanatics. Particularly if they involve spearmen beating tanks." I know, that's getting
really implausible, but still, I can dream.)