To visualise an ancient battle, it is important to understand the scale of the battlefield in Total War games does not reflect very well the actual extent of flat ground available in most parts of the world. Most places you go in the Western Mediterranean where these battles were fought have more hills, more settlements and agricultural land, and the ground is not so flat for such an extreme distance. Even a slight slope could give a defending army an enormous advantage and it was very desirable to take such a position whenever possible. Most armies also fought a short distance from their camps, and these were usually not too far from cities and towns, where the required resources for supplying an army can be found. Such things and other landmarks would be more prominent in such an eagles eye view of a typical ancient battlefield.

The sense of pace in the games is also completely wrong. Battles often lasted hours, and armies took hours to depart from camp and organise themselves into battlelines. Engagements also were more fluid and incorporated extended periods of rest and missile combat between bouts of hand to hand fighting. Armies did not just crash into each other and slug it out immediately except in very rare cases, and if such a charge was made the battle could end very quickly, but this was unusual. So an eagles eye view of a typical ancient battle should show a much slower movement of men and a much slower pace of combat of differing intensities at different parts of the battleline.

The formations themselves, due to the game mechanics, do not reflect real life formations. This is because an ancient general did not have an eagles eye view of his army and could actually see very little in many cases, due to dust and dirt kicked up by so many moving men, and if he could see well his ability to actually command and control his units were very limited. We should note that a single legion covered a frontage of several hundred metres, and more similarly sized groupings of men meant more such distances added to the length of the line. As a solid battleline could not be compromised by moving front line units, as this would present an opportunity to the enemy to penetrate and rout their opponent, units in the battleline did not move around from their original position during fighting. Only reserves such as cavalry or other dedicated units could be maneuvered, and these would usually be committed to fighting on the flanks or between the two infantry lines. For reasons of the difficulty of command and control such as I have described, most armies deployed in a single unbroken battleline of several ranks, spread out to avoid being flanked by the enemy battleline, and this formation could not substantially change during the fighting.

The whole idea of 'units' maneuvering on the field is also exaggerated in the game. Tribal armies were collections of warbands and personal retinues of widely different sizes that would simply line up next to each other. The Romans were unusual in that they had smaller units such as maniples and cohorts that deployed in multiple lines, but even then they generally avoided any complex manoeuvres. A lateral movement of a rearward line to one flank or the other was probably the most complex thing these secondary and tertiary lines did, aside from possibly moving forward to replace exhausted front line units. But again, for the most part armies formed up in single, solid battlelines with various collections of cavalry and light infantry fighting between and around these lines. Note that in the Empire, Roman armies also generally deployed in a single line.

Essentially, ancient battles were much slower and simpler than depicted in Total War. This was mostly a product of the very limited ability to exercise command and control over his army that an ancient general had after the armies had committed to battle. A real battle might see the two armies take several hours to move out of camp and deploy, so that they engage around midday. Skirmishers and cavalry would often fight this entire time. Once both sides were prepared, they would advance on each other carefully and gradually and fight in a relatively cautious manner, perhaps for hours, before a vigorous charge and close quarters fighting saw one army retreat or break and suffer heavy pursuit. There were countless variations on this generalized description I have offered, but the main point is that the manoeuvre of armies was a much slower, cumbersome and more careful process than is depicted in Total War.

Useful sources:

Goldsworthy, The Roman Army at War.

The Cambridge History of Greek and Roman Warfare, Vols. I and II.

Sabin, The Face of Roman Battle.

Southern, The Roman Army.

Zhmodikov, 2000 (forget the article name?)