With certain films the idea of giving a totally unbiased objective opinion is impossible to be honest. In this case, one's religious beliefs will have an influence over how one reacts to it - and like any adaptation of a universally known book/legend/mythology, those familiar with its little details are obviously going to get a lot more out of it than those who aren't. As an agnostic myself with neither any religious beliefs or real foreknowledge of the Jesus story, I can only speak from that perspective and so admittedly some criticisms I have here are undoubtedly things which those familiar with the text will disagree or not notice in their viewings as its part of the original story.
That said despite all the hype and controversy, "The Passion of the Christ" turns out overall to be something that completely surprised me - rather average. Visually its glorious with Caleb Deschanel's poetic cinematography and the utilitarian production design giving us something striking but never too grandiose. Ok so they go overboard on the slow motion shots but elements such as the costume design (this film has the swankiest priest outfits you've ever seen), the sets, the score and lighting make it all an admittedly atmospheric film (esp. in the first half), and the much debated issue of subtitles and speaking everything in the ancient languages of the time does nothing to detract from the story.
The fact is though from a perspective of someone only familiar with the basic elements of the tale, the straight forwardness of this film's tone and lack of back story make for an essentially empty adaptation lacking any real depth or emotion. This Passion is a coldly clinical take on Jesus' death - non-believers will be glad to hear the film is thankfully not preachy, but you are going to have a hard time catching up as with the exception of a few unenlightening flashbacks, we're thrown right into the brutal events of his last few hours with no explanation of how we got there and in many cases where we are. For example because I read other reviews of the film I know things like that the bald androgynous woman is Satan and that Monica Bellucci is Mary Magdalene, thank god for that because neither is clearly explained in the film (any adaptation should at least try an be accessible to those unfamiliar with the original source material).
Aside from the look of the film, it's obvious Gibson has put a LOT of effort into the movie and it's a very visible labor of love. The performances are the other thing that really define it with Caviezel and Morgenstern as Mary providing superb work in essentially one-note roles. Kudos should also go out to the effectively sinister androgynous woman, and the guy playing Pontius Pilate as he turns out to be the film's most interesting and multi-dimensional character. The others however aren't so good, not from acting but rather an understandable lack of development. Bellucci is reduced to staring off into the distance, Jesus' close disciples from Judas to Peter are over before they really begin, and Caiphas and his priests are baddies in an almost Hollywood tone (I was almost expecting evil laughter). Assorted villagers scream or look sad, assorted Romans grit their bad teeth and throw whips - not much too it.
The flashbacks, which are a short but welcome relief to the rest of the film's draining tone, attempt to provide a little insight into the power of Jesus and his messages but aren't particularly clear in their intent. In them however we do find one of the film's few emotional pulls - that of the love of Mary & Jesus. A scene towards the end of the film where she tries to help her fallen son is a tear jerker mostly due to the aforementioned fine work of the actress. Surprisingly enough this is in opposition to the grisly 'scourging' scene where Christ is brutally tortured. The real nasty stuff begins about an hour in and from then on the entire film's tone changes.
The first half whilst convoluted and a little confusing for a non-Christian, has interesting elements and themes of betrayal, tragedy, love, etc. and visually changes scenery and look relatively frequently. Then comes the second hour which is where the tedium sets in. Is the violence brutal, yes. Overdone? To be sure. Shocking? Funnily enough no. The term subtlety isn't in Gibson's vocabulary, thus the violence is so graphic and constant that one becomes essentially desensitised to it - once that happens the rest of the film can be seen for what it is - a self-indulgent yawner. We know Jesus gets horrifically beaten by two Romans - why do we need to see it drawn out to ten minutes. We know he's forced to carry his crucifixion cross up the hill - so why then does Gibson have to spend a full half hour filming Jesus shuffling, tripping, being harassed by the guards, shuffling, tripping, harassed, shuffling, tripping, etc. over and over?
In a two hour movie a good 2/3 of the last hour could've been removed or better yet replaced with a better examination of the characters and Jesus' spiritual message whilst still leaving in violence and brutality cut in such a way that would've had even more impact than the gratuitous gore fest currently has. By taking the far easier option of displaying excessive violence than exploring spirituality, Gibson essentially lost the message he's trying to convey - so while we see what happened to Jesus, we understand very little about why. That leaves us as an audience bored rather than enlightened. This most human of tales is sadly lacking humanity.