Ah yes. In Civ4 there was no consequences at all, got it.
I know. What was the Stalin thinking?
I like you're use of word "suspect" - because I too have never been able to enter alliance with other AI regardless of how fair game and helpful I was to them. On the contrary - whatever good you'll do to the AI (like... Liberating them?) they'll end up hating you anyway. Possibly it was because instead of losing the game I was leading in some of the demographics.
Amazingly, some posters who defend Civ5 diplomacy think that in Civ4 if you've rested your cursor over a leader's name you knew what were they thinking about you.
I don't know about those "some posters" you're talking about, but I claim that Civ5 is simplistic in not fun way because your diplomatic choices are largely irrelevant. It doesn't matter what you do, if you'll cave in to them while disregard their blatant aggressive settling or army-waving they'll not declare on you for a bit longer. Game forces you to do warfare, and that's not fun.
Ah, and I'm bored to death to hear same phrases over and over again (Bismarck "auf intressen", Washington "trade of interest to you" etc), as well as watching their ugly mugs to see if they like me or not - and the thing that it doesn't really matter because it they're your neighbours they will come for you doesn't help either.
In my opinion biggest problem with Civ5 is that it's BORING. None of the previous civ games was putting me off like two weeks after I've played them. That there's no real choices, terrain doesn't matter and it's either army grind against braindead AI (I agree with you on this one) or clicking next turn all the time.
1. In Civ IV you could get away with almost anything because of the predictability of the AI leaders. Just push the right button, and you were home free. I don't know what Stalin was thinking, and I find it less than relevant in this discussion.
2. I've never tried to form a mutual defence pact with any leader because I never saw the point in it. It would have entailed obligations I was not ready to assume. As I said, in Civ V you have to be *real* and not just say one thing and do another. All the same, I am fairly certain Montezuma (in more than one game) was interested in entering into a pact of mutual support and conquest with me, no doubt lasting until we were the last men standing. But I don't like playing domination games, so I never tried wooing him back to the same extent.
3. I think a big problem with being able to "liberate" leaders of other civs (not city states) is that, as you say, they simply take up where they left off ages ago and probably will hate you. I think that once a leader of a major civ is dead, he or she should stay dead. I hope they tweak the game so that happens. I also think there should be a very slow process of assimilation - maybe two thousand years, four thousand years - after which a captured city simply becomes part of your civilization.
4. You could tell what a civ leader in Civ IV was thinking about you by resting your cursor on the leaderhead. More precisely, you could tell where he was heading. Going from "friendly" to "pleased" to "cautious" to "annoyed", as a rule because you were becoming too powerful or too successful. It was, as you perfectly well know, extremely easy to know an AI leader's attitude to you. It was all very simplistic. There were a few exceptions - Catherine was ready to backstab you at any time no matter how pleased she was, Gandhi would never attack you and Shaka and Montezuma could go from pleased to furious at the drop of a hat; but their respective mentalities were well known and hence also very predictable. And their actions were often quite stupid, like Shaka or Montezuma sending a huge army across an entire continent simply to bug you because you were the militarily weakest civ on that continent. They hardly ever gained much from it, but you knew they were going to do it.
5. The diplomatic choices in Civ V are far from irrelevant. I know that from having played the game and tried various strategies.
6. I agree that the vocabulary of the various leaders should be enlarged, though it's not high up on my list of priorities.
7. I also agree that the terrain should entail more penalties. Charging uphill with cavalry should, for example, not go unpunished.
8. I don't think that Civ V is simplistic or that there are no choices, and I definitely don't regard it as boring, though it does need more patches and balance tweaks. Clearly, we disagree about that. It's no big deal.