Here is the short version of what follows: sever ALL Tolkien's written works and The Lord of the Rings movies from this film, and you'll have a decent fantasy flick with some writing flaws to get over. Skip to the concluding paragraph of this review for the summation.
Here is the long version (and this is condensed to the highlights):
Despite riding the success of the enormously successful Lord of the Rings trilogy, The Hobbit is not a series that was made for fans of Tolkien. At most, The Hobbit appeals to casual fans of The Lord of the Rings movies, or fans of large-scale fantasy movies in general. That is not to say that the final movie is dreadful, though as much could be said if weighed by its source material. Since going into all the ways that The Hobbit: Battle of the Five Armies fails to represent Tolkien's work would require about four hours of discussion with purists, today I choose the easy route and will only judge the movie as a movie. That being said, I can't promise that my knowledge of the book and companion literature will not pop out every now and then.
Battle of the Five Armies picks up at the exact moment that The Desolation of Smaug leaves off. As such, the first ten minutes of the movie are wrought with glorious moments that reach heights of cinematic greatness. In this introductory sequence, the great dragon unapologetically lays waste to Laketown, sending its citizens into a frenzy. While the great dragon could not have been more beautifully portrayed, most memorable is Smaug's satanic taunting of the bowman Bard. One of my movie companions described this moment as "chilling" before going on to point out the absurdity of launching a harpoon from a weak makeshift catapult. As much as it is possible for a dragon to smile, Smaug smiles with unadulterated malice behind his flashing amber eyes as he seethes to Bard "you cannot save your son. He will BURN!" All at once there is reverence and utter terror at the great beast. And then a few scant moments later, it's over. The great dragon has been slain, yet two hours of movie lie ahead.
What could fill the next installment of The Hobbit when the dragon, a centerpiece of conflict, is dead before the movie's title displays onscreen?
Word of the dragon's demise spreads faster than dragonfire, and before long the inevitable scuffle for the rights to the mountain begins. Bard and the people of Laketown ask for the prize that Thorin promised them, which they now desperately need to rebuild their lives following the ruin of their hometown. The serpentine elvish king Thranduil desires to reclaim some Elvish jewels hidden within Smaug's glorious riches. The dwarves want to move back into what was once their home, and Thorin wants to hole up there forever until he finds the Arkenstone-- an heirloom of his dynasty. Thorin's old nemesis Azog the Defiler is marching an army of orcs/goblins right towards them, while his lieutenant Bolg brings yet another foul army from a far region. Meanwhile, Lady Galadriel, Lord Elrond, and Saruman launch a rescue mission to save Gandalf from a most unfortunate captivity. Amid all this, one of Thorin's dwarves has fallen in love with an elf. It's all a grand mess.
Where is Bilbo in all this? Really, this movie is less about the hobbit Bilbo, and more about the greater conflict. At times he almost seems relegated to the "best friend" category of relevance, relinquishing center stage to Thorin as the leading man. That is not to say that Bilbo is insignificant or that Thorin is not superb when in the spotlight. Quite the contrary, I would readily pronounce Martin Freeman's Bilbo and Richard Armitage's Thorin as the standout performances of this installment, along with Luke Evans as Bard and Smaug (at least for voice-acting). Freeman's impeccable portrayal of the quirky hobbit feels authentic and natural, true to Bilbo's somewhat comedic character, yet still leaves room for Bilbo's character development to be convincing. Thorin easily stands out for his perfect representation of consuming madness and obsession over the treasure. The movies grander moments come at the hands of one of these two characters. And make no mistake, there are certainly striking moments in The Battle of the Five Armies, but...
...While there is no lack of good acting, it can't always cover weak writing. The "love story" emphasized here is born of a rather short conversation shown in The Desolation of Smaug. That exchange is truly the only foundation for what becomes a superfluous side-plot that distracts from the main conflict and stirs the sort of drama that echoes the worst sentiments of lesser literature (usually of the kind involving vampires). Kili, one of the youngest of the dwarves, has fallen hard for Tauriel, and is less than coy about it. Tauriel returns the sentiment, but due to racial issues instead chooses to go on a mission with Legolas, who has his own romantic inclinations towards Tauriel. In a strange and misguided effort to win her over through pity, he takes her to a desolate land where an evil army is gathering, and gives a dramatic line about his mother dying here. This pointless errand serves no purpose but to temporarily remove the pair from the central conflict so they can re-enter the story at the most convenient moment possible, and contribute to the saving of the day. Without giving away too much, suffice to say that the conclusion of this odd triangle merely confirms its irrelevance.
Books and source material aside, The Battle of the Five Armies is difficult to judge well if weighed against the Lord of the Rings movies. While in fairness they are different stories, The Hobbit trilogy takes great pains to tie itself to Lord of the Rings and be taken just as seriously, while trying to be distinct to itself. Yet it would seem that a chronological viewing of The Hobbit and The Lord of the Rings would weaken the gravitas of the latter, rather than strengthen it. Early in The Fellowship of the Ring the audience learns that Saruman has turned evil, but The Battle of the Five Armies eliminates the possibility of that being a surprise. Strider in The Fellowship of the Ring is introduced as a mysterious and perhaps shadowy character at first, but The Battle of the Five Armies' completely gratuitous reference to him lessens that uncertainty as well. Certain events and relationships involving Legolas in The Battle of the Five Armies undermine his character in the Lord of the Rings movies, reducing the long-held racial issues between dwarves and elves to a juvenile bitterness over a crush gone wrong. All in all, The Hobbit trilogy creates multiple issues of continuity and various implications on plot for The Lord of the Rings if taken as a whole, and creates more questions than it ever answers.
If The Hobbit movies could be entirely separated from The Lord of the Rings movies, detached from writings of Tolkien, and made an entirely independent fantasy franchise, it wouldn't be half-bad, but would still fail to stand out beyond its genre the way that The Lord of the Rings or Pan's Labyrinth do. Rather than expand upon this point I'll just summarize it to this: depending on how you define fantasy, it could be well-argued that the genre in general has had a tumultuous relationship with quality, and has not commanded much respect or necessarily reached great heights of movie-making. Therefore, to say that The Hobbit succeeds as a fantasy movie is actually mediocre praise.
Assuming the audience hasn't read the book, The Battle of the Five Armies is no more or less than entertaining on a summer-blockbuster level. Those expecting the sobriety and pathos of Lord of the Rings will be disappointed, but those looking for something more on the level of The Chronicles of Narnia will be impressed. Those looking for an exciting family movie will enjoy it, but those wanting epic battle and struggle will probably yawn. As a fantasy movie, The Battle of the Five Armies is not necessarily a paragon of its genre, but with a willingness to overlook certain missteps in writing, and closing one's eyes to the constant insistence that The Hobbit movies are part of Lord of the Rings, it is hardly the blight of its genre either. It's okay, but not nearly as great as it thinks itself to be. I'm not sure I'd be eager to see it again, but I'm not sorry to have seen it once.