For my last four hours, I dabbled with a number of mods, playing Fall From Heaven 2 for about two hours, and then four ones for somewhere between 15-45 minutes each. I'm not normally so noncommittal when it comes to Civ4, in that I could have easily played any single mod for six hours straight and not considered the time wasted, it's just the combination of factors from my particular circumstances had me in a very indecisive mood (basically I'm drop dead tired from birthday-related disruptions to my normal sleep schedule).
The first mod I played was the Fairy Tales mod which was promising, but unfinished. I'm not marking this as a complaint or anything. It was obvious that an incredible amount of work went into it, but there were things like incomplete and misleading civopedia entries that gave it an unpolished feel. Also, through no fault of its own, it suffered the fact that it was in the same genre as Fall From Heaven 2 and thus invited comparisons it could not possibly live up to.
Because Fall from Heaven 2 is amazing. Quite possibly the best mod of any game, ever. Because it's not just a fantasy reskin of Civilization 4, it's a complete reimagining of the game's formula wrapped in an incredibly rich and detailed fantasy world. It introduces things like asymmetrical factions that have dramatically different gameplay mechanics (like the Kuriotes, who can only have 3 cities, but compensate by being able to work a larger area, or the Grigori, who spawn "adventurer" units instead of the normal great people). Its spellcasting system is a complex strategic and tactical challenge in its own right, with different spells being available at different levels of mastery and depending on what mana you have available. And the world around you is both more dangerous and more rewarding to explore, filled as it is with monsters and treasure-filled ruins.
The list of things I could compliment this mod on goes on and on. It's got a full compliment of lore-based scenarios with unique victory conditions (one of them has you hunting through the wilderness, attempting to collect a menagerie of captured animals), a level of presentation that is slick and appealing, There's even a fun little card game you can play to boost your relationship with the AI. It's just incredible.
Unfortunately, I couldn't get too deeply into it because I was keenly aware of the fact that the last time I got sucked into a mod, it ate up 10 hours of my life. Also, FfH2 doesn't work too well at quick speed. The enhanced, dangerous map is calibrated for epic speed, and if you play on quick mode, your technology and building falls out of sync with your adventuring and exploration, and it's not quite as satisfying. On day, when I have the time, I'll want to go back and do a properly epic Fall from Heaven game, but today is not that day.
Anyway, Gods of Old I noped out of when the AI hit my city with an earthquake for no reason and I realized I didn't want to try and navigate its weird religion system. Charlemagne, I played for about 3 turns before I realized that I really don't care for the advanced start mechanics (I didn't spend my points effectively, and wound up with a bunch of really weak cities). Heroes of the Three Kingdoms, I played for a little longer, and from what I saw of it, it looked really good, with a lot of custom assets and some unique army management mechanics that makes legendary commanders like Cao Cao both valuable and tactically interesting, but then I ran out of time, and I was like "if I wasn't so tired, I'd play this all night, but since I am, it would be pointless of me to stop and restart after the 20 hours is up."
Because while I love this game, and probably do have near-unlimted endurance for it, I've been playing it in one form or another for 60 hours already, and still have 20 hours to go, and I'm running out of things to say about it. Still, if you have the Beyond the Sword expansion, you should definitely check out Fall from Heaven 2. That alone will justify the price of the game.