Every genre has its litmus test for separating the self appointed true fans from the unwashed masses. The test is usually quite simple: if you like X, you're not a true fan. You're a poser, a pretender, just another wannabe who doesn't understand what [insert genre here] is really about. These true fans are the gatekeepers to true fandom, the steely-eyed and neckbearded guardians that protect their beloved stuff from the heathens.
For the last decade and a half or so, metal had nu metal, though the looming specter of Babymetal has made even Linkin Park acceptable by comparison. Science fiction has, well, pretty much anything published by Baen, since reading their stuff makes you a homophobic racist sexist ageist humanist istist, to hear the true fans tell it. For anime, the litmus test has become Sword Art Online.
Sword Art Online, or SAO, for the uninitiated, starts off as the story of a virtual reality MMO that traps its players in the game and, crucially, kills them in real life if they die in game. The story follows the protagonist, Kirito, as he works with other players to clear the game and escape. Which they do, eventually, only to have a series of other adventures where the virtual world presents a real life hazard.
SAO has become one of the most popular anime in recent history, right up there with Attack on Titan in terms of public visibility, and naturally, the true fans hate it.
Exactly why they hate it varies from source to source. Some claim that the story is unoriginal or uninspired, or that it's been done better since. Others take umbrage with Kirito, who they say is an overpowered Marty Stu with no character development. Still others critique the production values, that, despite being generally outstanding, are somehow still not up to snuff. The list goes on and on and on and on. I could probably squeeze a few thousand words out of simply describing the many ways that the true fans hate SAO.
The question is, though, does it deserve it?
In a word, no.
I'm not going to try to tell you that the plot of SAO is the best ever, or that aspects of it haven't been done better since. Log Horizon, for instance, got much more in depth with the combat system, something that SAO only glanced over. Grimgar of Fantasy and Ash ramps up the emotional stakes to unheard of levels, deftly blending hope and despair over some pretty nifty fight scenes.
I'm also not going to pretend that Kirito is the most interesting character ever created. He has his moments, but mainly he's a walking plot device that serves to advance things when needed. His main utility is being absurdly badass.
So SAO is not the best anime ever. Got it. It is, however, one of the most fun.
Where SAO excels is setting up set piece fights, backstopped on either end by emotional moments. You don't care so much that it's all patently ridiculous, or that maybe Kirito isn't the best character in the world. Not when he's blocking bullets with a lightsaber or dealing out delicious payback to the villain of the arc. The fight scenes are uniformly excellent, even if there's not much suspense because we know Kirito is going to power his way through them.
But good fight scenes in anime are a dime a dozen. What SAO does that so many others don't is get the viewers emotionally invested, and then having that investment pay off. Kirito might be kinda dull as a character, but that makes it easy for the viewers to project their emotions onto him. He's not quite the Gordan Freeman style silent protagonist, but the effect is similar. When he bonds with other characters, the audience bonds with them as well. And since the other characters are far more interesting, it works.
That's why, when the boss is defeated and it's time for the big emotional moment, you're hooked. You've felt Kirito's rage and terror and his desire to protect, because they're partly your own. And now that it's over, you feel the joy and the relief. The show encouraged you to get invested, and it rewards that investment in big ways. Personal triumph, tearful reunions, lives saved, friendships forged and romances kindled, all of this plays out in what should be a silly show about people stuck in a video game.
That's what gives SAO its staying power, and why it's remarkably popular years after other technically more impressive shows have faded into obscurity. And that, I think, is why the true fans hate it so much. SAO resonates with people, whereas a show like Log Horizon or Overlord might execute the premise of real folks trapped in a game world more competently, but fail to capture a wider audience. And that's why, in a decade, you'll still be able to find SAO merchandise in Hot Topic, while only hardcore otaku even remember the others exist.
If you haven't seen SAO, it's worth a watch. Maybe you'll love it, maybe you'll hate it, but either way, it's worth seeing what all the fuss is about.