I've seen very few 4x games in any genre where the diplomacy is what I would consider good. The AI is often capricious and arbitrary, and seldom rationale. There might be a long list of modifiers you might be able to see, but there's little dynamic to them. Improve relations by bribing or gifting, or by signing a treaty. Relations get to a certain point, and you can sign a Non-Agression Pact, followed by a non-bedwetting agreement, consummated by an Alliance.
If you betray an ally, you might get a reputation ding for the rest of the game, as you are untrustworthy. But I bet if you spend a few hundred gold, you can offset that penalty. It's kind of silly.
But that's not the way diplomacy works in the real world. The United States couldn't declare war on England even if it bloody wanted to.
Why hasn't anybody ever come up with a more intriguing model for diplomacy in a 4x game, where attitudes towards other countries often evolve despite your government's intentions? And where betraying an ally earns you more than just a slight distrust penalty from everybody else?
Am I alone in thinking there must be some other model out there, somewhere, that might be vaguely more interesting and strategic than "If you give me enough gold, I'll sleep with the wild pigs outside your second-largest city"?