While I agree with the sentiment that the victory conditions need work, I'm not sure this diachronic approach Dale suggests is the way to go. The classic victories (with the possible exception of cultural) all have the advantage of a clear "finish line" that makes intuitive sense. When you win, you know why you win: it's because you've conquered the world, or colonized Alpha Centauri, or been elected President of Earth, or whatever. It's not because you've crossed some abstract and invisible threshold.
Dale, when you complain that victory is based on end-states and does not measure how well the player played, I'm not sure where you're coming from. In any game of skill, the end-state reflects overall play quality implicitly. The sport of baseball doesn't need to directly reward teams for high batting averages or the number of steals, because these qualities all contribute the the one number that does matter: the score.
So I say keep the victory conditions simple and understandable, but rewrite them so that pursuing them results in actions that makes more sense. For example, the Civ4 cultural victory is really counterintuitive: building a wonder in any city except your three culture supercenters is a major opportunity cost, and to be avoided if at all possible. And conversely, building Hollywood in a city that's already going to hit legendary turns before the other two was also a waste. The game needs to find a balanced way to reward all cultural achievement, just as the space race victory rewards all scientific progress and production. I haven't played CivRev, but its "20 cultural events" version of the cultural victory sounds like it would do the trick.
Or, for something a little deeper, imagine an adjustment to the culture system: your cities spread your civilization's culture into all foreign cities they're trading partners with, in amounts depending on their overall cultural output of course. This could serve as a simple replacement for espionage: the more of your culture is in a foreign city relative to its native culture, the more you can see about that city. Also, the city's war weariness against you would be higher, and perhaps a "reverse war weariness" could produce happiness when diplomatic relations between the two civs are good. (I'm not sure this is entirely realistic: look at attitudes toward America in the modern world, either despite or because of America's cultural hegemony. But it's intuitive, and rewards good play.) Cultural victory is achieved when your culture is stronger in each other player's territory than their own - specific metric to be determined.
Since this mechanic works through trade routes, it encourages exploration and trade agreements. No longer can you sit on an isolated island and somehow dominate world culture without ever meeting another civilization! (Yes, I've done this.) In fact, I can even see this form of cultural victory subsuming the diplomatic victory, which would neatly kill two birds with one stone, since the current diplomatic victory system is also horrible. The diplomacy-culture exchange could work both ways: foreign citizens like you more the more of your culture is in their city, and your culture spreads more effectively the more those citizens like you. And the new United Nations might, oh, cause all foreign cultural spread in your cities to be automatically returned in kind.
So that's my brainstorm. I'm sure there's plenty of room for improvement, but I think it's at least the kernel of a good idea.
EDIT: Imagine oppressive forms of government are more effective at stifling the spread of foreign culture - perhaps even providing options for removing that culture. This would make the propagation of liberal values through diplomacy a natural means to the end of cultural victory.
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