I never seem to build more than 4-5 cities now, and i am reluctant to keep those i capture
When building cities i ignore nice land with fish and cows etc...land i would have jumped on in BTS, i only build by resources or luxuries now
The result is a lot of untouched land late game.
Do any of the top players build lots of cities?
This one is annoying because it is so persistent so let me take the time to address it:
Your assumption is a common mistake and a myth. Many players have drawn the conclusion that because each new city penalizes you, large empires are a bad idea. It appears very few have actually looked into the numbers behind this because if they did they would realize continuously expanding is not only viable, but desirable.
Here's the kicker: That 5% science cost increase per new city is compared to
if you had only one city, not the total size/output of your empire. The same applies to the culture cost increase. Thus, in a 20-city empire your 21st city only marginally increases technology cost and policy cost - not the 5% and 10%, respectively. So, late-game expansion is still viable. This is even more true, of course, if you have an empire that's already well suited for expansion - say, playing Rome with the Order ideology and Liberty policies.
Typically, a new city will require just a handful of population (5-7) and a Library to not slow down your science, even in a modern era scenario. This late in the game, that can be achieved in short order just by shipping food from one of your trade units and purchasing the Aqueduct, which creates a city with rampant growth. This has the benefit that using a food trade route to this tiny city is far more efficient than sending it to one of your established science cities which, in spite of their higher multipliers, suffer from requring several hundred food units just to grow one population point. When this new city then adds a few more points of population and a University it is already significantly speeding up your progress, not to mention how you now have this new base giving you extra production, gold, etc.
The only reason to temporarily not found more cities is generally if you're aiming to lock down some national wonders. Civ V does heavily penalize expansion but this 4-5 city 'empire' talk is pure nonsense. The only caveat is that some players like to set up their games with extremely favorable conditions (re-rolling maps etc) and this can create games where the science rate is so fast new cities won't have time to do much at all. Perhaps it's because these forums have so much talk about such games that these misconceptions exist? In realistic scenarios where you aren't simplying aiming to break the game, though, expansion is always worthwhile.
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With regard to the actual topic: Civ IV is the [much] better game. However, Civ V *with* expansions became quite decent and V adds a number of new concept that are valuable - city-states, for instance. Civ V, despite its popularity, will always remain a shadow of what the game
could have been had the developers actually bothered to create a proper AI for this multi-million-selling title, though.