The isekai genre is tremendously popular in the present-day anime industry, a little too popular some might even say. It's nearly impossible to ignore its widespread fame, as a fair share of all the new anime released every season are bound to be some sort of isekai. As a creative genre, it didn't become popular overnight, but slowly over the years, and Sword Art Online is one of the few shows which heavily influenced the rise in popularity of this type of anime.
Across its three (technically four) seasons and nearly 100 episodes, and a movie, like any other long-running series Sword Art Online has gone through many story arcs. Some of these arcs are almost universally loved by fans, while others have faced their fair share of criticism. Taking everything into account, this list attempts to rank them as fairly as possible.
9 Progressive
One of the biggest criticisms against one of Sword Art Online's most beloved and first arc, Aincrad, is the lack of time it dedicates to the development of many of its characters. The light novel series Progressive was a method of rectifying that mistake, by providing more detailed accounts of the events of the adventures of the characters, namely Kirito and Asuna. It has been ranked last by default as it has set to release in 2021, but if it turns out to be anything that the novel readers are expecting it to be it is without a doubt gearing up to be one of the greatest arcs in Sword Art Online.
8 Calibur
Caliber is considered a part of a collection of side stories that take place in either Sword Art Online or ALO and is the shortest arc in the series. Nearly all important supporting characters make an appearance for the quest of a lifetime as Kirito and the gang join up to find an all-powerful in-game item called the Holy Sword Excalibur.
The arc provides some background to the world of ALfheim Online and contains a surprising number of references to Norse Mythology. As great as the fanservice is, it is mostly filler and the sword which is what the whole arc is supposedly about is never used at all in the anime.
7 Fairy Dance
While Fairy Dance is certainly not a bad arc as a whole, it has some certain controversial and abysmally executed elements that make it unwatchable for most fans. Anime has never shied away from portraying strong female characters as they are, and Asuna is certainly one of the best. Sugou Nobuyuki is not a good villain on his own merits and comes off as just a worthless creep. Fairy Dance throws all of Asuna's badassery out the window and turns her into a complete damsel in distress for the sake of the plot. And the scenes including her and the tentacles are best not spoken about.
6 War Of Underworld
Character power levels are greatly inconsistent, unnecessarily sexual scenes featuring female characters and just poor writing overall makes War of Underworld a subpar sequel to one of Sword Art Online's best arcs. As the finale to one of the longest-running arcs in the franchise, it certainly has many commendable epic and climactic moments, but a proper look under the surface reveals too many problems to be ignored.
The animation has never been more beautiful and fluid, but flashy visuals can rarely ever compensate for weak writing.
5 Phantom Bullet
GGO introduced one of the coolest looking and strongest villains in the series, Death Gun, and also brought in one of their longest-standing and combative characters to date - Sinon. But other than that the arc doesn't have much to offer. Guns in an anime that literally has the word sword in the title that has always been about fantasy sword-fighting feels forced. Not to mention at the end of the day Kirito ends up fighting with a sword anyway. And Kirito with long hair in breastplates is not a look fans have ever much appreciated.
4 Ordinal Scale
Every episode and arc of the Sword Art Online anime was adapted from a light novel, except Ordinal Scale which was an original movie from the author himself. Detached from the main storyline and taking place between the second and third season it revolves around a newer virtual reality system, Augma. A combination of great visuals, fresh settings, and more adventures for Kirito, Asuna, and the rest all make it one of the best entries in Sword Art Online's long history. By focusing on a premise outside its typical virtual worlds, the movie allowed the characters to shine even in the real life.
3 Mother's Rosario
Mothers Rosario has been hailed as one of the best written and most emotional arcs of Sword Art Online. While it is a fantastic story in itself, with Asuna in the lead (something the audiences have always wanted), the arc doesn’t fit into the overall storytelling of Sword Art Online and feels out of place in a second season that already lacks direction.
But it makes up for this by delivering a heartfelt story that highlights Asuna's charm as a character. The events of the arc don’t have any actual consequences, but it’s a good example of how a completely new character can be made into one that fans will never forget.
2 Alicization
Alicization was the breath of fresh air the Sword Art Online needed desperately, as many fans will agree undoubtedly. With a completely new world and characters, it quite literally restarted the franchise in a manner of speaking. Alicization introduced a multitude of new characters like Alive and Eugeo who quickly became fan favorites and added depth to Kirito as a protagonist. Although the fact that many of the established cast was sidelined didn't sit right with many fans, overall it is regarded as some of the finest storytelling in Sword Art Online in years.
1 Aincrad
Sword Art Online very first and arguably its best arc, Aincrad is a great example of what superb storytelling looks like. No matter what direction the plot goes in the future—such as outer space, which is exactly what the last season's ending hinted at—its debut arc will always be the definitive Sword Art Online story. The series simply wouldn't be where it is today in terms of popularity if its first arc hadn't been so well done. It had the right amount of everything: action, drama, colorful characters, and a hint of romance in a setting that was greatly unique and inventive for its time.