Warning: Since the mystery is pretty much what a Scream film is all about, this review contains major spoilers not just for Scream 4 but for Scream 1 and 2 as well. Be forewarned!
The secret to the Scream formula is that these films play at half a dozen games, and win them all. That's a major reason why this franchise is so popular, you can watch them for a variety of different reasons and still come away satisfied.
First, and perhaps foremost, they are world-class "whodunit" stories in the age-old tradition. Where everyone is a viable suspect, and you won't know until the end who's good, and who's evil.
Secondly they are, of course, brilliant deconstructions, which is arguably what made Scream famous. It took a genre awash in cliches and injected a spark of awareness to make it all feel new again. It was a quintessentially 90s idea, the Nirvana of horror films, so it's no surprise I love it.
But the deconstruction is about more than just a hip eye-wink to the audience. How many horror films exist in a universe apart from the horror culture that we fans live and breath? How many zombie movies are there where no one has heard of George Romero, and the walking dead are called, well, the walking dead and never "zombies?" How many classic slasher set-ups are there where the kids never bother to realize they're the unfortunate recipients of a tragic archetype?
As a horror fan, if I ever found myself living in a by-the-numbers horror scenario, movies are the first thing that would come to my mind. How could they not, with them being such a part of my life? And that's where Scream comes in, to rectify that perplexing lack of awareness which makes so many horror films feel slightly disconnected from the real world we live in. That's why films like Scream are such a hit with hardcore horror fans despite taking their share of cheeky 'stabs' at the cliches of the genre, these are films that connect the fandom of horror with the medium of horror.
Thirdly, the Scream films are the two things they're supposed to be, the two genres they're born from. They're the all-time ultimate "teen scream" genre films, full of hip dialogue, drunken parties, sexy characters and teen angst. It's also beyond question the highest quality slasher franchise in 20 years, full of creative kills, intense chases, and doomed ingenues.
Unlike other fun horror films like Shaun of the Dead or Dale & Tucker Vs. Evil, Scream is fun but it's not a comedy, it's a horror film that takes itself seriously and even delivers a couple of decent scares. Come on, all alone in the house, the killer calls, but wait, he's in the house! The intros are always pretty darn creepy, admit it. One who is so inclined could ignore the deconstruction, and even the mystery, and just enjoy these films as slasher films. And they'd still come away with a good experience.
Lastly, in regards to the Scream series... Not being a veteran slasher fan, I've never really had one of those iconic killers to call my own before, but I have to say I've grown very fond of Ghostface. The creepy voice, the obsession with horror films, the meticulous planning, he's a fantastic 'character,' even if technically he's someone new each time. And that signature move he has when he turns his head to the side after a character says something to him, is just fucking amazing. Despite being a mask, it totally gives this powerful impression of mock-concern, almost pity. It's such a simple little thing but whoever came up with that was a genius.
Now on, specifically, to Scream 4.......
The concept that Scream 4 is a makeshift, in-universe reboot of the original Scream in addition to another sequel is what really kept the mystery fresh and alive for me. That's because you have all these archetypes from the first film (and some, even, from the second film -- I was definitely looking at that one nosey reporter with suspicion during her one short scene), except it's impossible to know which of the archetypes are going to pan out as they originally did, and which ones are going to be turned on their head. So you have all of these obvious killers and yet you still have no idea who it's going to be. This gave Scream 4 a dimension of ingenuity where it feels like we're treading on uncharted territory instead of just being the fourth iteration of the same set-up. In other words it doesn't feel cheesy ala "really, everyone gets caught up in the same kind of murder mystery AGAIN?" when (in-universe) the killer is intentionally recreating the past again and (conceptually/on the filmmaker's meta level) the film is intended as a tongue-in-cheek way to win new viewers, many of whom would not have been around to watch the original Scream 15 years ago.
Some people have complained that the film isn't modern enough. Admittedly it definitely appeals a lot more to original Scream fans than to newcomers characters like Dewey and Gale are never even fully explained (as far as their history goes), so newcomers would probably feel at least a little in the dark. But what's wrong with Scream appealing to the classic formula? If they wanted to do a true reboot they'd probably have named it Scream Again or Scream Louder. People complain so much about modern horror, is it so wrong for one film to hearken backwards?
More importantly, though, I think the movie's classic 90s feel was intentional, because it's another piece of the deconstruction, and it actually helps to make the film relevant to today. It's a pseudo remake, after all, retro is the idea! Even when they aren't remakes, retro horror has been very successful recently, with period films such as The House of the Devil, Paranormal Activity 3, and Let Me In. So rather than detracting from Scream 4's relevance, its bygone style actually marks it more clearly as a comment on modern horror.
And that gets into what makes Scream 4 so special for me, individually. The original Scream films played on the slasher classics of the 80s. Scream 4 ingeniously arrived just as dozens of modern remakes of these classic slashers started pouring out of film studios. But the remake craze isn't restricted to slashers, remakes of all kinds of creature features and exploitation films joined in as well. And Scream 4 was able to perfectly nail the tropes of all these silly remakes, really down to a T. I've never been an avid fan of the classic slashers, so the original Scream films only tangentially connect with me on the deconstruction level. But I'm quite familiar with these modern remakes so Scream 4 makes an intimate connection with me.
The only mild criticism I have is that it feels like they should have 'gone for broke' and made this a climactic finish to the series, maybe even kill off a major character. Instead, they had their sights on rebooting the franchise and following through with more sequels. Unfortunately, Scream 4 performed below expectations, and the idea for further films has been scrapped. Even so, I have to admit, had new films followed, that would have been worth a lot more than the shock & awe of killing Sidney or another major character in Scream 4. As badass as it would have been, nothing's better than more Scream films, and a Scream film without Sidney, Gale, & Dewey sounds like it would be hard to pull off, quite possibly a "jump the shark moment."
In hindsight, part of me wishes the killer had turned out to be Sidney, because her motive and backstory would be by far the most compelling. The film definitely started to build it up with her whole arc about not being the victim. Well, in a slasher, you're either a victim, or you're the killer. After sustaining atrocity after atrocity in her life, it's plausible that Sidney could have developed a need for murder in order to prove to herself that she's not powerless, that she in fact wields the power to end a life. Sidney Prescott has actually killed several people over the course of the series. It's always been strictly in self-defense, but killing that many people has to change a person, it could reasonably have germinated a taste for murder inside her.
Of course had the series continued, it's possible the plan was to eventually make Sidney the killer, perhaps with Gale as her accomplice. Part of me thinks Kevin Williamson is too sentimental to go that route, and I can respect that. If they went that route but they failed to pull it off excellently, if it ended up kind of cheap or weak, then that would retroactively damage the rest of the series for some people, by ruining the Sidney character. Of course if it was pulled off really well, it would add a whole new dimension to all the previous films. On the other hand, it might just be too cheeky and brutal for the Scream franchise. As Scream 4 very aptly quipped, "the unexpected is the new cliche," and the Sidney-Gale killer ending would very much play into that.
All in all this is one of my favorite horror films by far. Don't just rent it online, buy or rent the DVD, because it contains an extended version (with a different chain of events) of Britt Robertson's intro scene. I wish she had been cast in one of the main roles, her snarky precocious style (not unlike a young Katie Holmes) was perfect for Kevin Williamson's writing (perhaps she could get a gig on The Vampire Diaries). It also contains an extended ending with an interesting tone. And it contains a bunch of other deleted scenes, one or two of which should definitely have been included in the film because they expound on the deconstruction aspect, and those are always the best scenes.