The Romans, and to a lesser extent, the Greeks, always had one person who had the most power, a Figurehead if you will, nearly every government had this, regardless of what type of government it is.

Julius Ceaser was the Ceaser in Rome and carried much power, but he focused on conquering land so every one was okay with, except the people who killed him.

Chancellor Palpatine was the head of the old republic in it's dying decade, while traditionally the Chancellor has little direct power, Palpatine granted himself emergency powers during the war. Only to serve his own agenda

Darth Vader was the face of the Empire, and while he did wield enormous power, he was really just a pawn to the Emperor.

The Ethereals, over many years, amassed an army of different alien species from sectoids to cyberdisks, they are the ultimate leaders of the cllective, but there are hits of a higher power.

The One Earth government had many high ranking metahumans, from wonder woman to yellow lantern, but all authority was beneath the high counciler, Superman.

This week the only new topic that we could conceive was ‘weapon comparison.’ Which is ridiculous given that the romans used medieval weaponry, spears, axes, sword, metal shields, while the cultures I have been researching use far more advanced weaponry, ranging from modern weaponry, Projectile weaponry and gunpowder based grenades, (the UNCS and Xcom), While others use a wide variety of energy weapons ranging from Plasma (The Alien collective,the combine ) to Tibana gas based lasers (The empire, The CIS, The Galactic republic) to Crystal based energy blades (The Jedi, and the Sith). 
Even their armor is vastly difference, The Romans use standard metal armor, which is still a good method, Xcom uses it, the CIS uses it, however, just metal is outmoded now. The Empire and the old republic use a special plastic like polymer for their armor. The Combine and the Ethereal collective use some element that doesn't occur naturally on Earth. The UNSC and the Combine use basic Kevlar and other modern materials. Megacorp use a mix of titanium alloy and nano-technology and electrical currents to redirect damage. Much more complicated than normal metal.

A sword.

A UNSC gunpowder based projectile weapon

A Heavy Plasma rifle, Used by the Ethereal collective and later Xcom

A Tibana gas based blaster rifle. Used by every star wars military.

The Overwatch Standard Issue Pulse Rifle (OSIPR): a dark energy/pulse-powered assault rifle manufactured by the Combine.

Lightsabers. Laser swords based on focusing energy through a lightsaber crystal. naturally comes in blue and green and can be synthetically grown in red.

Greek armor

The MJOLNIR armor, (the Spartan armro) an advanced, and expensive, suit providing protection against everything except drowning.

The phase I armor. Effective and recognizable, with an easy rank  denotation system relying on arm and helmet color, but bulky and uncomfortable.

The Phase II armor, more comfortable and easily modified for specialist troopers.

Storm-trooper armor. Cheap and easy to mass produce.

Basic Xcom body armor, easily obtained, but weak compared to the enemy's. essentially a bottom tier armor for Xcom.

Xcom's top tier armor, A complicated and advanced piece of armor that actually increases one's Psycic abilities, while decreasing the affect of enemy Psi attacks.

Basic Combine soldier armor, relying on thick padding and materials,  Primitive, yet effective

Carbonox armor. The best Megacorp has to offer to a consumer who needs an expensive advanced military grade armor. use thick plating and nano-technology to negate 90% of all damage received, regardless of the source.

Disclaimer: I do not own these picture, all credit goes to respective owners.

So far the Romans seemed to show a typical representative democracy, each region (Planet, State, Universe, Etc,) elected a representative to represent them in a 'Grand council' of sorts, to vote on bill in advantage of their region. A common government type, used in the Galactic republic, The CIS, The Federation and to an extent the Galactic Empire, but underneath the Romans showed a world of deceit and backstabbing. A rotting core hidden underneath a beautiful mask. This is surprisingly common in representative democracies, with the Galactic republic in its final days succumbing to corruption. Some however, like the Empire, Didn't try to hide. They already ruled galaxy, what did it matter?

Roman Senate

The Republic Senate

Disclaimer: I do not own these pictures and all credit goes to the respective owners.

Recent research has shown that the Romans had a circular population density, meaning that they were most dense in the center in Rome and nearby cities, and consistently getting less dense the further away it was. This form seems like it would very common, but surprisingly, there were not many examples of this, only The Galactic republic, the Galactic Empire and the Federation. But there were few examples of a different population density, some had equal spread, such as the Borg, most had no rigid population chart. However, this is not as much they had a unique population density as it was not enough information. The Combine for example, only have one documented territory, as no one has traveled to their other territories and returned, with the exception of members of the Combine themselves, and they aren't very talkative about this. Others, like free Polaris and the Solana governments have no population density charts that have been released.

Roman city

Coruscant skyline

The star wars galaxy

Disclaimer: I do not own these pictures and all credit goes to the respective owners.

Recently I have begun studying the similarities and influences of Greek and Roman culture. so far I have mainly focused on one society. The Old Republic. They are surprisingly similar to ancient Greece and Rome. First, politically, both were representative democracies, focused mainly on senatorial representation, with one main political leader selected from within the senate. Military is a mix between Rome and Greece. They do rely on the method of having large numbers of organized troops, who make up for individual weakness with numbers and organization, namely, clone troopers. However, they also use the Greek method of having a relatively small number of incredibly skilled warrior, such as Spartans, most notably I the republic with the Jedi and certain clone commandos. Actually, almost every military has an 'elite' commando.

Greek
Spartan

Mandalorian Clone commandos of the Old Republic

A Bx-Series commando droid. Armored in an advanced alloy and remarkable AI.

An Urk-Hai: a tougher and smarter breed of orc. Were saruman's Shock troops during the 'ring ars'

A Predator: One of the greatest hunters known to anyone, able to hunt anything from a Xenomorph to a Basilisk Leviathan

A Cyberdisc: A advanced and surprisingly organi robotic warrior, armed with advanced energy weaponry, grenade launcher and thich armor makes this one of the toughest and deadliest soldiers in the Ethereal collective

(Disclaimer: I don't own either photo, they belong to their respective owners,)