Except the civilization still DOES have the same leader - YOU. While you might rationalize your Civ leader doesn't live for 6k years and instead has various descendants who take his place, the fact is the same guy - yep, still YOU - who sacked that city a few thousand years ago is still calling the shots and setting out the master plan.
So the idea that AI wouldn't judge you by actions you did earlier in the game because some figurehead leader you imagine was running your country at the time is now dead is nonsensical to me.
A human player will still hold a grudge with you not only for what you did to him earlier in this game... but what you've done to him in previous games. If anything they should go this way with the AI and have it track data like that.
This is kind of the reason I made this point. It's against anyone who wants to cry for "realism". As soon as you have one leader who lives for thousands of years reality goes out the window (personally this would be my preference, I have real life for reality, I want a video game for fantasy).
Yes a human player will still hold grudges (and yes hold them over many games), but a human player will also recognize a beneficial trade and accept (unless he's so ticked off that he'd bite his nose off to spite his face), which is something the AI doesn't do unless the trade is severly lopsided.
Also comparing multiplayer games to single player ones is a little off. In a multiplayer game everyone is trying to win, whereas I don't get that sense at all from the AI during a single player game (admittingly I don't play multiplayer civ, I prefer marathon games, too hard to organize, best I can do is a succession game with a buddy of mine). So if I were trying out a multiplayer game I'm going in with the mindset that
everyone will eventually backstab me, whereas the predictable AI I know who will and who wont.
There are many people you've probably met in your life who've made a bad or even just less than stellar first impression. Some continue to behave in the manner that made the bad impression and our opinions of them never change. However there are those who we either just caught on a bad day (ours or theirs) and we realize over time that it was more of an occurance and not their normal behavior so our opinions of these people change (the opposite is also true, meaning going from good to bad).
My contention is that the AI is placing too much emphasis for too long on an "occurance" that was outside of the normal behavior of a given player during a game, and one that wasn't repeated.
I, on the whole, like the warmonger mechanic. I just believe it should be tweaked to have more complex applications of it. If given the choice of having it in it's current form, or not having it at all - I would actually rather have it as is. However it is a negative impact on a player who during most games usually only has one early war (when empires are small, 1 or 2 cities) and maybe 1 late one out of boredom while I wait for a victory condition to finish (if I even finish a game at all, usually I deem the game "won" and begin a new one, much like 2 foot "gimme" putts in golf - again I prefer marathon, finishing off a game that is, in the bag so to speak can really test the patience of hitting "next turn")
Sure, track game data for AI's, but then you do have to realize that the player's data should be tracked for each civ he plays as strats are going to vary (ie, probably not going domination with Pedro, but Genghis is going to go scorched earth)