Well, I somewhat inadvertently won a diplo victory on Turn 391 with 2033 points and a rank of "Lincoln". Ramadamadingdong built the UN, and the Victory Conditions menu said that there were 21 city states and I had 10 votes and needed 10 to win. So I figured I needed to vote for myself to at least tie with Rama...but instead I won, 10 votes to Rama's 7. I suppose I didn't count the votes all that closely, and apparently Rama had fewer than I thought. More on this later.
SO...I reloaded from an autosave and this time around I voted for Hiawatha instead, which was just enough to make sure nobody won the UN election and let me keep playing. I finally won cultural after clicking "End Turn" a bunch of times. I didn't realize I needed to save the file after winning, so I don't have a savegame of this win, but I'll try to attach a renamed autosave from 4 turns prior. Orleans will complete the Utopia project in 4 turns, the next UN vote is in 5, and unless Rama nukes me (he won't) there's no way for me to not win in 4 turns (which is what happened.) The reason I am not posting a post-win save is...it takes about 5 minutes to load the file, and a minute in between clicking "End turn" which is all I would be doing, and that's just not any fun. Anyways I finally won a cultural victory on Turn 449 with a score of 1896. [Edit: and rank "Churchill". We would of course have preferred De Gaulle.]
(In fact, I won ANOTHER inadvertent diplo victory on turn 441 with a score of 1903. I wanted some additional food to help Orleans build the Utopia Project faster, so I bought out one of Siam's maritime allies. Well, turns out I bought out one of the only sources of uranium on the map, so all the city states who wanted Uranium suddenly leaped to my support, and I won the upcoming UN vote even while voting against myself. Once again reloaded from an autosave so as to keep playing for the Cultural win...)
Gameplay: I built Paris and Orleans, took Thebes and Memphis from Egypt because I thought I needed a seaport (turns out I didn't and Memphis was a largely useless city). I unpuppeted Thebes after a while as the governor made some good build choices and I decided I wanted another city. As discussed in my "In Progress" report, Songhai made an awesomely smart move and got a whole bunch of citystates so pissed that they declared war on him, allowing him to take over my key cultural ally (Florence) and one of my maritime allies (Venice) while saying "Whoops, sorry, I didn't mean to attack your friends, they attacked me." So I was forced to crush him in order to liberate my friends. (Too bad he had pikes and I had rifles and arty.) Hiawatha joined in the fun but didn't actually accomplish anything; however this kept Hiawatha as my nominal ally the rest of my game. ("Hey, when d'you wanna finish off that evil Askia, huh big chief Nappy?")
Social Policies: Honor, Piety, Patronage, Freedom and Commerce. I finished Honor relatively early, then used the 2 free Piety SPs to grab the culture-promoting policies from the Freedom tree. Knocked around between Piety, Patronage, and Freedom for a while, delaying finishing any of them...I was thinking that when I finished 3 or 4 policies the AI would see what I was doing and attack...apparently I needn't have worried. By the time I was on the Commerce tree I was getting a new SP every 8 turns or so. I spammed Landmarks all around Paris (and what the heck, why is the Landmark one of the most boring tiles in the game?) and towards the end was using GAs and whatever GPs I got from citystate allies to start golden ages...I think I was in a golden age for most of the last 50 turns. I think one of those was happiness-induced.
[Edit: Cristo Redentor was a big help, as was having Hermitage in Paris (+250 or so culture per turn from Paris, with I think 4 or 5 landmarks being worked plus the Hermitage and various cultural buildings.) Rama actually built the Sidney Opera house...actually I am at a loss as to what Siam was attempting to do. They could have won 4 different ways (diplo, beat me to cultural, domination, or space - and didn't do any of them - and not through any effort on my part, either.]
AI:
Rama conquered his continent eventually but clearly [edit: I guess?] was going for the UN win. [Edit: I kept getting messages from everyone about how we needed to act now to take out the domination-driven Wu Zetian!...all the while Siam was slowly creeping across the map, taking out Chinese cities. Things that make you go "hmmm".] Now having written some glowing praise of the AI in one instance (backhandedly going after my CS allies)...I gotta say, the AI still played extremely poorly. Siam had a bankroll of something like 30,000 gold and clearly could have bought out every single CityState on the planet if he had wanted (whereas I was making +150 a turn in golden ages and about half that normally.) And yet he allowed me to block him something like 5 times at the UN vote. He was far more advanced than me in every respect and could have, if not wiped me off the map, at least delayed my plans further...but he never attacked (despite referring to me as a "puny civilization".) He had all the uranium on the map locked up as well. Against a halfway decent player I would not have won this game.
Final thoughts: Military allies are actually far more helpful than I thought. After I bought out a bunch of military cities in order to block Rama from the UN victory, I basically stopped producing military they were giving me so many units. I basically paved over most of my production and food tiles with trading posts and relied on just buying citystate allies for the rest of the game. One question, though - seriously, a unit that costs 500 to 1000 to purchase, if gifted to a city state, only nets you 2 influence points? Really? I do think there should be some decay from a gold gift, but 2 points? That's it? Admittedly I was gifting back units they gave me that I didn't want, but still. Also, how come I have some allies gifting me paratroopers, and others gifting me lancers? I kind of like that the city states don't all advance at the same tech rate, but that degree of disparity is kind of...weird. I also encountered a situation in which a CS ally gave me a Great Scientist. I wanted to use him for a golden age but that ally was in the middle of foreign territory with no open borders agreements...so there was no way for me to get him into my territory to use for a golden age. Was this intentional? Seems kind of stupid...I would think the allies should be able to get the units they are gifting you into your territory, at least!
One of my puppets actually built the Apollo Project. I read the poster who said they had trouble with the Utopia Project because one of their puppets started building it. How DO puppets choose what to build, anyways? This seems more than a little strange.
One last thing: I remain extremely disappointed with the design of this game, which is so unbelievably terrible that as I am playing it I wish I had the developers sitting next to me so I could punch them in the face and demand they pay me for being a beta-tester. Very, very stupid designs such as: the pop-up notifications which show up on the right side of the screen, which must be right-clicked to remove them, BUT if you right click just a hair off the popup, the autoselected unit then receives that as move orders to that far-right tile! The sheer lack of thought that apparently went into the design of the UI, the graphics (orange circles for production and yellow for money, THAT'S not hard to tell apart) and all the rest leave me seriously disappointed in this game. I sincerely hope that Firaxis will endeavor to fix this behemoth monstrosity they have released. This is not a matter of patching a few issues; this title needs a FUNDAMENTAL OVERHAUL in order to fix game design mechanics which are fatally broken. When (or if) Civ 6 comes out, rest assured that I will wait at least a year before buying it, and I will buy a (legal) used copy of the game rather than laying down cash for a pristine version which I no longer trust to be any good. Congratulations Firaxis, you've lost my business.