I'm not sure how it is in the US, though I imagine given the demographics, it would be similar or even slightly more pronounced than it is in Canada; which ever weekend happens to contain the Easter holidays (Good Friday, Holy Saturday, and Easter Sunday) will feature television channels jam packed with "The Ten Commandments", and just about every film produced in the middle of the decade that has anything to do with Jesus. It is a fixture of the season, as sure as fake green grass, brightly coloured stuffed animals, and sickeningly sweet confections consisting of chocolate or marshmallow. The most striking thing about them is how utterly similar they are; in cinematography, in costume, in direction, in score and especially in message. Or at least one message: The god of Abraham is the best, any other deity can suck it.
Alright, so this ought to be patently obvious, this is how monotheism works after all. Our god is the best and only god, other people are idiots for worshipping anyone/thing that isn't our god. Alright, and so it makes sense also that the costumes are going to be similar, after all they all take place around the same time... Except for "Ten Commandments", which is supposed to be taking place during the events depicted in Exodus. So they substitute golden helmets for ones with ridiculous plumes, but other than any given actor in TC could walk by a shot in, say "Jesus of Nazareth" or "Barabbas", and you'd never know they were from a time period several thousand years prior. This may seem a little nit picky, but it conveys a sort of unconscious understanding of the continuum which Christians believe exists between Exodus and their own Gospels. A separate issue in and of itself, so lets just focus on the other glaring similarity (and purpose) I mentioned earlier.
So, and again fairly obviously, these films are supposed to provide entertaining reenactments of various Gospel (or OT) narratives. As such they are going to have the bias inherent in the world view of the source material, and of course this would necessitate that the religious or theological perspective come along with it. These stories are familiar, these stories are known, these stories can probably be recited by a not insignificant percentage of the population. However, these films lack the full breadth of someone to both interpret and understand them (i.e. a religious officiant) for the audience, and so must be able to convey their message in as obvious and self evident manner as possible. Also they need to be entertaining, have self contained narratives and be able to fit into an allotted time slot. What this translates to is that they haven't got the entirety of the NT to flesh out perspectives on things, and so tend to be really "on the nose" with portrayals of certain things: Roman religion, Roman society, Roman culture, Romans, Christians, etc.
Which brings me to my first point that is irritating coming from a polytheistic perspective: Whenever a Christian character begins to speak about "their Lord" to non-Christians, everyone becomes utterly transfixed by their words and by their desecration of all other deities. There is usually some sort of half-hearted defense made, which generally amounts to, "what makes your god so great?", which is followed by the Christian answering the question, dashing to pieces said defense. When this is interrupted, it is usually by some Roman official of power/influence who, not offering a theological argument, mentions that Christianity is outlawed and so the Christian has to be punished, usually by capital punishment. The pertinent points which come across in these scenes, and the overall films are as follows:
1. Pagans were monsters.
2. Pagans had no theology.
3. Pagan deities do not exist.
4. Roman religion can be explained as little more than "Worship of the Emperor".
Pagans were monsters
In these films there are generally four types of Pagan: the master, the plebeian, the slave, and the convert.
The master is fairly self explanatory, they are the characters who have some degree of control over the Christian characters, as well as the plebes and converts. They are the face of the "Roman machine", the one mentioned above who will end the witnessing of the Christian, not through theological points but by the use of their power, generally through force. If they are shown to be religious at all, it is only for personal gain or politics; often secretly shunning the superstitions of the plebeians. As such they are power hungry, amoral and oppressive.
The plebeian is your average Roman citizen whose only interaction, or point in the film, is to stand in a crowd and encourage violence. That's it. If these films were all we had to represent our knowledge of Roman culture, we would think that all Roman citizens did was watch gladiatorial combats and give the "thumbs down" for every single contestant who lost a duel. Where the master will use violence to gain power or maintain order, the plebeian loves violence for entertainments sake. Blood thirsty and ignorant masses.
The slave is any character who is not a master or plebeian, nor Christian (nor Jewish), who will not be converting to Christianity by the end of the picture. They are usually the only voice trying to raise a defence of Paganism, and the same who are utterly silenced the moment the Christian character speaks. Slaves, but on the "wrong side".
The convert is a slave (and very rarely a plebeian) who was a Pagan, but will convert to Christianity at some point. Usually any Pagan character who has any sense of morality, or who may try to help the Christian, will inevitably convert, recognizing the inherent emptiness of the Pagan position. Slaves who see the light.
To synthesize these rough categories into understanding the way the Roman world is portrayed, Pagans were terrible, violent, oppressive and superstitious. Any "good" Pagan will ultimately convert to Christianity, thereby robbing Paganism of any redeeming figures.
Pagans had no theology
At no point, in any film, is Roman religion ever actually discussed (other than point 4). No attempts are made to explain, or explore the deep theology and mythology which underpinned Roman religion. Instead we are treated to a glancing mention of the civic nature of Roman religion, that it was little more than an apparatus of the state to ensure control of the ignorant masses, and the the idea of freedom of religion was unheard of. This theological vacuum is, of course, why everyone on screen (regardless of role) is at least temporarily transfixed when a Christian talks about his deity. Paganism was hollow and so anyone within ear shot will have to listen to the wisdom and truth spoken... until Christian is maimed/murdered.
Pagan deities do not exist
Not that any of the perspectives here come as a surprise, but this is necessarily self evident in the world view being put forward. Monotheism simply does not allow for the possibility of the existence of any deity except the one the adherents worship. Within the films we are almost certainly guaranteed at least one example of some character, usually the master, slave or convert, seeking the aid of a Pagan deity (because again, in a monotheistic context, and Paganisms theological vacuum, the only sort of prayer which exists is petitionary). This is usually in the context of either trying to show up the Christian (whose prayers are always answered) or saving themselves; in every event, and at every attempt, failure is the only result. Of course it is, because those other gods don't exist.
Roman Religion = Emperor is God
What is important here is noting that the idea of the civic virtue of making an offering to the genuis of the emperor is not what is being portrayed. What is portrayed is that the Emperors (who ever they may be) are portrayed as believing themselves to be gods, or are seen by the masters, plebeians and slaves as being a god. It is an allegorical tool, emphasizing the difference between the true, disembodied, Christian god and the crass, all too human, Emperor. Again, not terribly surprising considering how much the symbolic Rome is utilized by the authors of the Gospels, Acts, Epistles and Revelation as being the exemplar of everything which is wrong with "this world" and so in these films, the Emperor becomes the living embodiment of everything which is wrong with Rome, and by proxy Pagans.
That is pretty much my summary of how Pagans are portrayed in such films. I'm not going to be providing a step by step explanation of why every one of the characteristics is either completely wrong, or at the very least an egregious distortion of actual history. If you're interested in rebuttals and the like, and aren't already aware of them, just do a quick goolge search for "roman religion". Or you know watch Gladiator (not a great film, but decent enough in its snippets of ritual, and certainly its ability to portray Pagans as moral) or Agora (although the problem with this is the tit for tat portrayal, which needed to be grossly exagerated to provide "balance").