When you choose a civ and a leader, you pick the following:
- 2 starting techs
- 2 traits
- unique unit
- unique building
Four out of six are defined by civilization, two by leader. However, the leader traits seem to have most importance in shaping the grand scale of the game. Starting techs make huge difference early on, UUs may or may not make a huge difference in some specific era, UB usually provides a slight advantage, the later the UU the greater the advantage. Synergies between UU, UB, starting techs and traits of the leaders available for the civ are debated here on the forums, and opinions to all directions are certainly to be found.
However, when an AI is considered, there's one more aspect: the leader personality.
When adding a new leader, you have to add it to some civilization. In general, the leader is expected to be a historical figure with significance in his era, and a representative figure of the civilization in question. Most of the leaders currently included are well known (at least to people with some sort of education), and all can be found in any reasonable encyclopedia - electronic and bound alike.
When a fitting leader has been found, the traits have to be assigned. These should relate to the characteristics of the leader, although often these are assigned per his actions - our knowledge about the actual character of the person is often quite limited. Some trait combinations aren't acceptable as they may have too deep synergy leading to over powerful combination, and most trait combinations are debated on the forums here.
In addition, the AI personality has to be programmed. I haven't looked into what all this consists of, but based on the feeling I've gained from playing, this is more of tweaking a relatively small number of preference values than a full fledged personality program.
And of course the leaderhead, graphics, and leader specific wordings of diplomatic options added.
I would say that having two to three leaders per civilization from the official source (that is, Firaxis, in form of the core game and expansions) is enough. Modders have provided numerous additions, as it should be (I'm not really familiar with those, as I don't use nor much care about content mods - this may change in time when I feel something of specific interest to me has appeared on the scene).
I would actually go as far as to say that the leader traits are too big a factor when choosing the civilzation and leader I'm going to play. I would feel more comfortable with higher emphasis on civlization, with leader being more for flavour than strong game balance issue. However, that's something for Civ5, as Civ4 is quite set in stone having been released to the wild.
On WWII:
Yes, it was indeed a huge, destructive war that blanketed the globe in smoke and gunpowder. But looking back, what all was due to specific leaders of some nations, and what due to general development? If there had been no Adolf Hitler, how much would've changed? Would another person have risen, the grand scheme of things already moving to the direction, to take the place Hitler held? Or was it Hitler that moved the world? Asking these questions, not only regarding Hitler but other people in positions of importance as well - which of the occurences were due to specific people, which due to the tide? And which of the leaders were great, which just figureheads?
Of course same questions can be asked regarding many of the leaders already in cIV, and many of those proposed.
During WWII, I feel that few of the national level leaders made many decisions without those decisions having been first formulated by larger groups of people - whether by council of generals or a civilian cabinet. I would almost go so far as to say that the time of the great leaders had passed - no single person was shaping the world really. The world had changed, with too many fields of science, too many sources of information, for anyone to manage alone. It was not Hitler, it was him and his cabinet. It was not FDR, it was also the cabinet. Churchill? Who made him a leader - UK had a monarch (although there's a strong case for Churchill instead of the King). Stalin? This may be the closest to dictatorship, but even Stalin wasn't alone.
This could of course be debated, but regarding cIV I stay behind my stance: no leader of any kind from recent past (which I've defined as 100 years, which should be enough that the player community wouldn't have personal experiences from the time, very few having second hand experiences either) should be included. Where an interesting debate could be held regarding WWII, and my opinions could sway one way or another, a fact is that it's too recent to not have emotional effect on most of us therefore leading to more subjective than objective choices.
. Ok, maybe he would've got shot a bit later but things would've gone a little different then I imagine.
