Differences announced so far in Civ 5:
- No Religion (Will probably be implemented in an expansion).
- No Tech trading. Instead you form tech pacts with AI that boost both yours and their research output by 15%. This is meant to reduce the incentive to simply trade all an opponents tech and then attack them, as attacking means no more 15% bonus.
- Hexagonal tiles and only one unit per tile. also cities now defend themselves.
- Civilizations will have truly unique bonuses like in CivRev, rather than the two minor improvements they get in Civ 4.
- Minor civs will be on the map and can only have a single city. You can take over the city, but appeasing and defending them will give you more rewards. They also add tension between normal civs - one major civ might favor a minor civ, another might hate it, and this relationship with minor civs will transfer over to affect diplomacy between major ones.
- No Religion (Will probably be implemented in an expansion).
- No Tech trading. Instead you form tech pacts with AI that boost both yours and their research output by 15%. This is meant to reduce the incentive to simply trade all an opponents tech and then attack them, as attacking means no more 15% bonus.
- Hexagonal tiles and only one unit per tile. also cities now defend themselves.
- Civilizations will have truly unique bonuses like in CivRev, rather than the two minor improvements they get in Civ 4.
- Minor civs will be on the map and can only have a single city. You can take over the city, but appeasing and defending them will give you more rewards. They also add tension between normal civs - one major civ might favor a minor civ, another might hate it, and this relationship with minor civs will transfer over to affect diplomacy between major ones.