Tough call. It also depends on criteria:
You can easily argue that civrev is the worst in the series. However, I do not go that way, because 1) it's design philosophy, platform, and target audience were all different from "civ 1-5", and the nomenclature essentially treats it as a spinoff. Technically, it is still a "version" of civ, but comparing it to the others in the series isn't apples to apples.
The other reason civrev can come out ahead of the others is that, on release, it has fewer broken mechanics, UI problems, and other such issues. Granted, that might be because the design was less ambitions, but when compared to IV/V on release it is still a more complete game because compared to those, it worked...better :/.
As for my vote, people might be surprised after my outcry over civ V that I actually voted for civ IV. Let's take a look at why civ IV was borked/stupid beyond belief:
- Just like civ V, my biggest complaint was that the game prioritized graphics over gameplay. IV was not even a single drop less bad with this than the travesty that is V, and so IV makes no headway here.
- Just like V, IV throws bonuses at problems rather than addressing them, ESPECIALLY in vanilla. The AI was awful...before BTS, it had no VC plans whatsoever and would blindly roll DoW or eventually make space (inefficiently and unplanned). In BTS, its only plan was a shoddy culture attempt unless you used mods. On top of that, IV vanilla handed out some of the most ludicrous bonuses ever (BC liberalism wasn't out of the question for the inefficient AI!) and let outcomes rely on a combination of nigh-perfect play...and a heaping helping of luck. Luck-based outcomes have continued to be an issue through BTS 3.19 and civ V, but it is obscene in civ IV vanilla.
- WORSE than civ V, the user interface 1) lied to you and continued to do so through 3.19 2) had permanent issues with unit selection and micro, that also persisted the entirety of IV's existence (and does even now) 3) could allow such nonsense as units moving before you can give them new orders, ACCIDENTALLY declaring on an AI, without prompt, without pressing a single key, and accepting proposals mid term by clicking somewhere before the trade screen even came up. Civ V persists in UI problems and they remain an inexcusable disgrace for a top-line franchise, but bad as they are now, they were and are atrocious in civ IV to the point of losing players who play at a decent speed games due to things that they never, ever ordered happening. Civ IV is the crown ruler of ridiculously awful interface, so bad that even something like V can not touch it.
- Strategic imbalance: How quickly the forum forgets. BTS did two things: it WEAKENED high-level AI bonuses and improved it's whip/anti-rush AI. Before BTS, one of THE most common strategies was axe rush (they were not even weak to chariots...............................). In other words, THE strategy on high levels was to beat the AI's bonuses by killing it with military before it could defend itself. Other strategies were doable, but largely uphill in comparison. Does that sound familiar to people who dislike the same reality civ V (me included)? It should. Just because V repeated a mistake IV made doesn't mean the original IV gets a pass.
- Civ IV hides information from you or forces you to repeat actions un-necessarily over and over again, only relieved by mods. V actually does this too, but it's largely a push.
Adding the eventual insults of giving us new features in each of the 2 expansions while not correcting core gameplay issues/bugs and NOT EVEN TESTING the new features pushes civ IV down even worse, but even without those factors, IV vanilla was one of the worst releases in franchise history, probably the single worst. Civ IV was saved by expansions (a little bit) and by mods (a lot more). Civ IV started off as essentially a beta release much like V, and has remained an incomplete game to this day (if you dare argue with me, check how UN resolutions being picked or vassal state mechanics or the AP victory works and try again). Unlike IV, V has a small glimmer of hope possibly, because they're not done patching it. Technically, they're not done patching IV either, but I'm not holding my breath.
