Top Ten Sword Art Online Arcs

From what I've seen Aincrad is the most popular arc of the franchise, but more or less, the second or third choice for best arc is Mother's Rosario. In my opinion it's personally, THE best arc of Sword Art Online, of all time. It's a short arc only consisting of seven episodes and was really just a side-story to fill up Season 2 of Sword Art Online, but that sure doesn't mean it's just "filler", if you miss out on this arc you've missed out on half of what made SAO a masterpiece. The happy intro song and the tearjerking outro song defines this arc.
It's about a girl known as Konno Yuuki who suffers from AIDS and is going to die very soon, but before it she wants to create a happy final memory with her friends, defeating a floor boss on New Aincrad so that their names can be shown on this leaderboard thing. But they're not very strong, despite Yuuki, being the strongest swordman in all of the franchise, they need someone more, so they challenge random players after player to see who is worthy of helping them. It turns out it's Asuna Yuuki, one of the main SAO heroines who is chosen. Now this arc starts out very slow, I will agree. First three episodes..., eh a bit boring. Then..., it quickly becomes my favourite arc ever. The emotions, the story... Don't get me started on the last episode, which is the best and saddest episode I've ever seen.
This arc does unfortunately though contain my least favourite villain, and it is a villain who exists in real life as well, AIDS. Yes, the illness, AIDS. It's technically the villain of the arc because it killed Konno Yuuki, my favourite SAO character. Ok..., maybe not a "villain" but you get the point. It's definitely the best SAO Arc though, due to the emotion, plot and the excellent writing of Konno Yuuki.

Overrated unfortunately. It is heavily carried by the setting and world concept, with the actual story feeling clunky and disjointed. None of the story arcs make a coherent piece, and the finale could have been inserted as the fourth episode without any real changes to the outcome. Kirito and Asuna are the only characters with any meaningful characterization or arcs.

Oh yes, the classic, the original that started SAO, Sword Art Online and the main reason people still watch SAO despite a handful of terrible arcs. I mean if Fairy Dance came first, the universal opinion of SAO would be different. The premise of this show was originally "If you die in the game, you die for real". This is the premise that made SAO so interesting in the first place, and all of the SAO arcs that have some kind of actual danger element to them are the ones that are pretty good.
This arc in particular is such a classic. It introduced most of all of the characters we know such as Kirito, Asuna, Klein, Silica, Lizbeth and Heathcliff. It's a very awesome arc but one huge flaw is the pacing. In Episode 1 and 2, we're on Floor 1 of Aincrad, in Episode 3 we're already at floor 22! And in the next episode we're at Floor 47 or something like that! Seriously? And just four episodes later we're almost at the end of the game! WHAT? It's too quickly and we get to barely see anything of Aincrad but a few handful floors. And then the arc ends anti-climatically at Floor 75 because Kirito found out that Heathcliff was actually the game's creator, Akihiko Kayaba.
Speaking of which, the villain of the arc is Akihiko Kayaba / Heathcliff, the creator of the game and he's a pretty interesting villain. SAO isn't known for having good villians but this guy is widely accepted as the least terrible because his motivation is slightly interesting (although he forgot it) in that he locked up a bunch of people in SAO so see how they'd handle themselves in a game if they knew it meant life and death.

Ordinal Scale is the only SAO arc that's not based on any of the original light novels by Reki Kawahara, although it got adapted into one after the arc's release. This isn't part of any season, instead it's a full-length movie taking place between Mother's Rosario and the Alicization season. It's about two hours, or roughly as long as half of the Mother's Rosario Arc. It's INCREDIBLY well-written and interesting though.

A new engine called the Augma is released which allows for Augmented Reality games, such as Ordinal Scale, which has bosses from the original SAO game. But a dark secret then is revealed as the SAO survivors who lose agianst the bosses then suffer from an amnesia and it's revealed the creator of the Augma, Shigemuru Tetsuhiro is trying to steal memories of SAO from SAO survivors to revive his daughter Yuna, who passed away in Sword Art Online. Excellent villain! It sounds weird but trust me it's badass and amazing. One of the best arcs we've had for SAO.

This is a love it or hate it arc, as people who are huge fans of Sword Art Online typically have very high opinions on this arc, while some who only watched the Aincrad arc decided it'd be good to hate it because it's set in a world of guns. I'm on the loving side because of a number of reasons, but this is among the most interesting and exciting arcs of the franchise.
Basically some of the top players in the video game Gungale Online have mysteriously been killed in-game when they've recieved a gunshot, by someone who goes by the name Death Gun so the government of Japan asks Kirito if he could possibly find out the identity of this serial killer.
This story is so intersting and awesome! We meet Sinon here who is pherhaps one of the few very developed characters in the entirity of this series, Kirito gets a female avatar which adds for some hilarious moments and don't forget the fact he uses a LIGHTSABER for frick sake!

The villain, Death Gun is also my favourite villain in the series. Well technically it's two people. There's Shinkawa Schouichi who's a SAO survivor who played for the murderer guild Laughing Coffin. He's pretty badass but overall his character is slightly hollow. His brother, Shinkawa Kyouji is one of the most developed characters ever in the franchise. He's super creepy and unsettling, but at the same time you feel bad for him when he tells about why he does what he does. Overall, this arc is amazing.

Ah yes, Fairy Dance arc, AKA the lowest point of SAO. The fact that this came right after Aincrad, one of the best arcs is just humiliating. Everyone has already mentioned what made this arc so disappointing. Sugou Noboyuko (pedophile villain), Asuna's devolution, too much sexualization. There's also the incest romance where Suguha has feelings for his cousin Kirito, although that at least was handled decently. However there's another flaw of this arc, the boredom.
Kirito must just get to the top of the World Tree in the video game Alfheim Online to save his wife Asuna, who has been kidnapped by Sugou Noboyuki. CLICHÉ! There's not much sense of danger because you if you die in Alfheim Online, you'll just respawn. Unlike Aincrad, where the player's had to stay alive or else they'd die, or in Phantom Bullet, where a mysterious Death Gun was killing player after player. This arc is just so uninteresting. I don't hate it (surprisingly), I mean it's still SAO after all but it easily is my least favourite arc of the whole series.