Civ V is not a well-balanced game. This isn't necessarily a slight against it, depending on what you're looking for - Paradox games revel in being unbalanced, for example. However, I personally feel that in Civ V's case, it is a bad thing, because it is the sort of imbalance that limits choices, rather than creating them.
Let's start with the first - and biggest - problem, combat. The problem with combat in Civ V is that ranged units are absurdly powerful. Because of the way the system works, especially the Zone of Control rules, ranged units with a few melee defenders up front cycling in and out of position to heal can hold off a superiour force indefinitely. In the game's defense, it's hard to say if this is because the combat system is inherently imbalanced, or if it's just because the AI is so stupid, but either way it's a big problem.
Second, we've got the Civs themselves. This is entirely predictable - beginning with Civ 3, Civs have been growing more and more diverse - and that means less and less balanced. However, I would say that Civ V is the first game where there is a definite tier system in play, and I would argue that this is because in Civ V, the Civ distinctives actively shape the way the Civ plays. This can be a good thing or a bad thing, depending on your point of view. In Civ IV, most of the traits were transferable to a variety of victory conditions and playstyles. In Civ V, while the best Civs tend to have abilities that are transferable, most do not.
This is good in the sense that there is a lot more variety between the Civs, and playing one Civ will feel fairly different from playing another (though there is not quite so much variety as there is in a game like SMAC). However, it's bad in the sense that the power divide between different Civs is far larger than ever before, and there's a distressing amount of Civs who require specific map conditions, setups, and/or gameplay styles to be competitive - made even worse by the fact that there's quite a few Civs who are incredibly powerful in virtually any situation.
Personally, I prefer Civ IV's Civs. While I like the variety of Civ V, I feel that too many Civs are pigeonholed into either specific playstyles or specific map requirements. In Civ IV, the Japanese were arguably the worst Civ, but they weren't at too large of a disadvantage (and most of the disadvantage they did have wasn't from the Civ itself, but rather from their idiot personality's isolationist policies). In Civ V, the Danes are arguably the worst Civ, and holy crap, do they struggle.
For me, I see Civ V's Unique Abilities the same way I see a lot of changes the game made: Good idea, bad execution.
Third, the social policies. Social policies are like the definition of "Good idea, bad execution." When I first started playing the game, I absolutely loved the concept. You spend culture to invest in certain mentalities and values that define your culture - how awesome is that? But I ended up finding it inferior to not only Civ IV's Civic system, but even Civ 123's government systems. Why? Well, a couple reasons, but the biggest one is balance.
If you're familiar with Civ IV's Civics, that's a great case study for balance. Religion, Government, and I would argue Legal were very well balanced. Let's take Government: You've got Hereditary Rule, which gives +1 happiness per unit garrisoned in a city; Representation, which gives +3 happiness in your largest cities and +3 science from every specialist in your empire; Police State, which gives a 25% increase to production speed of military units, and a 25% decrease to unhappiness suffered from war weariness, and you've got Universal Sufferage, which gave you increased production from towns and allowed you to rushbuy things with money. All of those options are potentially very powerful and can be incredibly helpful in different situations. You are forced to make a choice. HR is great for growing, Rep is great for research and development; PS is important for wartime, and US is a fantastic tool for building and developing. Which do you go with? That depends on a lot of things.
However, Civ IV's Labor and Economic categories were anything but balanced. Let's take a look at Labor. We have Slavery, which allowed you to rushbuy with population; Serfdom, which made your Workers improve things 50% faster; Caste System, which allowed unlimited Artists, Scientists and Merchants and gave +1 hammer from Workshops, and Emancipation, which made your Cottages, etc, grow at double speed and spread unhappiness to Civs that weren't running Emancipation.
Here you don't really have a choice. Serfdom is flat out useless and will almost never be played, Emancipation is hardly any better and mostly only comes into play if the unhappiness penalty from other Civs running it becomes crippling; Caste System is potentially powerful for someone running a pacifist, specialist-heavy society, but even it is generally going to be inferior to Slavery - the ultimate powerhouse. There's simply nothing that can compare to being able to rush-buy things with your population. Grow your cities, discover a key tech, then in one turn whip out six or seven of the brand new units and use them to wipe the floor with your neighbour.
Civ V social policies (almost forgot what this thread was about, for a second), are like the Labor Civics. They're unbalanced to the point that you don't really have a choice. There are a few policy trees that are simply always optimal. No matter your playstyle, your civ, the map, you almost always want to go with Full Tradition->Patronage until Renaissance->Full Rationalism. This is the Slavery of SPs. 90% of the time, it's your best bet. Liberty and maybe Commerce are the Caste System of SPs: Hardly optimal, but still useful under certain circumstances. You might consider them the other 10% of the time. The rest - Honor, Piety, Exploration, arguably Commerce, Aesthetics - these are the Serfdoms. They're useless. There's no real reason to take them unless you want to challenge yourself (yes, even Aesthetics - it may seem custom-geared for a Cultural victory, but I'm not convinced that it's actually better for cultural victories than Patronage or Rationalism - Rat only contributes indirectly, but I would argue that getting the late game culture buffs earlier is far more useful than anything Aesthetics gives you). Usually if you do take them, it's only for the "opener" Wonder, and you never actually get any of the policies in it.
So, I guess, long story short: Civ V retains most of the balance issues of earlier games in the series while adding in a whole host of new ones, so I wouldn't call it a well-balanced game by a long shot. That being said, once again, balance and quality can be two different things, so depending on what you look for in a game, this is not necessarily a pejorative assessment.
) that one "best" way to play will eventually come out, I think. And if that Best Plan is penalized there will be a New Best Way. You're never going to get the table legs quite even.
