Hi, McBane, the main issue here would be what kind of unit we're looking for. I'm guessing you'd like to compare Spartan and Roman infantry, and if so, yes, their equipment was pretty similar.
The thing about infantry is that you need it to be heavily armed, and you need it to work in close-knitted formation, otherwise they will get slaughtered by any half-a*sed cavalry.
Ancient Greece infantrymen were called hoplites, and there was no great difference in armour between cities. Hoplites were generally heavily armed (carrying up to 50 pounds of equipment in battle), and worked best in the small conflicts between city-states. As Greek warfare grew bigger (think Persian wars and Peloponnesian wars), the structure of the hoplitic phalanges and the hoplitic armour began to change - these newer wars required greater mobility. The greater form of the hoplitic army was certainly the Macedonian phalanx, invented by Philip II (Alexander's dad). It was because of this heavily armed, highly mobile, and perfectly trained troops that Alexander was able to do what he did.
Hoplitic armour was not standard, because each citizen had to buy his own stuff. On shields, for instance, one would most often show some family symbol. A poor hoplite would normally just buy the basics - a spear (around 3 m in lenght), a helmet and a shield. Middle-class people could afford the linothorax (a sort of flexible breastplate reinforced with bronze or animal skins), while a richer person would go all the way and buy himself a bronze breastplate, a decent helmet with cheekplates, greaves and a second set of weapons. The typical hoplitic shield, the aspis, was 1 m in diameter and 33 pounds in weight (it was supported at the shoulder). They also carried a xiphos (short sword), or a kopis (curved sword), or both. There were several variants of helmets - the most popular one was the Corinthian helmet (first link below) and the Chalcidian helmet (a lighter version of the same thing, second link). Spartan hoplites tended to wear the Pilos helmet, a metal version of the traditional pilos cap (third link). All these helmets could be decorated by stuff on the top - the mst available material was horse hair, since warhorse's tails were cut off before battle to avoid it getting tangled in stuff.
As for Romans, you should remember Montesquieu's quote: "It should be noted that the main reason for the Romans becoming masters of the world was that, having fought successively against all peoples, they always gave up their own practices as soon as they found better ones."
The Roman army was based on heavy infantry, which had been 'copied' by Greek units. In the end, it proved more effective because a) most Roman soldiers were career soldiers, and didn't have another job (Greek soldiers were farmers and merchants who had to go back to their jobs or see their family starve - Greek wars normally laster 3 weeks), so they could be trained to perfection, and b) the Romans wanted to conquer the world and expand their boundaries, so they attacked virtually all their neighbours (Greeks considered war a necessary evil, and never had designs of empires - except for Alexander).
Roman weapons were adapted initially from Greek and Etruscan weapons. When they fought the Celts, they started mass producing Celts weaponry, and when they met Carthagians at sea, they built a navy just like theirs.
Like a Greek hoplite, a Roman infantryman would have a spear (pila) and a sword (gladius) as his main weapons. Other weapons they carried over the centuries were the pugio (dagger) and the spatha (broadsword). Also like the Greeks, some people wore no armour at all, while other wore heavy mail. Like in Medieval times, Roman soldiers had to wear protections under these chain mails, because they would have cut through the clothes. They had the advantage, however, of being very effective.
I feel like a could go on another 5 paragraphs, but this answer is already too long! :)
The thing is, Roman armies existed from 500 BC to 500 AD, and there is a lot of variety in these 1000 years! Just check the link below to see more kind of armours and more pictures.
In short, though, don't believe any movie, remember that Romans were master copiers and that the design of armours depend on the use you make of them - infantrymen were more or less the same all over, because their units had the same purposes.
Answered By: chrusotoxos - 11/17/2011