These days, Isekai is a prevalent genre, and a lot of these shows seem to involve video games in the themes. But let’s not forget one of the first huge titles that focused on a video game Isekai. Released in 2013, Sword Art Online (SAO) has had 4 seasons (the third season is split in 2) and a spin-off series, Gun Gale Online (GGO), and the storylines all revolve around fully immersive games.

RELATED: 15 Worst Couples In Shonen Anime, Ranked

The result is that Sword Art Online is one of the most popular anime series of all time, even if there are plenty of fans who hate on it. Still, the series is a massive enough franchise now that it's very possible to look at all the seasons and films and decide which parts are the best.

8 Season 2

Kirito and his friends reunite in Sword Art Online Season 2

Season 2 introduced a new virtual reality game, Gun Gale Online (GGO), and a concept pulled from the original season — players being killed in real life when they’re killed in the game. It also covered a story arc in ALfheim Online (ALO), introduced in the previous season, and ended with one of the most heart-wrenching arcs in Sword Art Online.

Unfortunately, despite the Gun Gale Online portion introducing a genuinely interesting video game world, it also felt like too much of a retread of the original series. The writing also features far too much fawning over Kirito, which makes the arc tiresome.

7 Season 1

Kirito and his friends pose on the promo banner for Sword Art Online Season 1

Season 1 launched a juggernaut anime franchise and caused the popularity of the isekai genre to skyrocket. The first half of the season, which focused on the virtual reality game that trapped its players, Sword Art Online (SAO), was mostly well-done, with some amazing visuals and plenty of neat vignettes that explained how the heroes were surviving in Aincrad.

The second half introduced ALfheim Online (ALO) which was a game that seemed less intense than SAO or GGO. Meanwhile, the series gradually started giving into some of its worst tendencies, including making Kirito a perfect character that everyone adored. Sugou might also be one of the most hated villains in anime.

6 Sword Art Online The Movie: Ordinal Scale

Asuna, Silica, and Lisbeth talk with excitement during Ordinal Scale, SAO

Taking place several years after season one, Ordinal Scale highlights a new technology introduced to the world, a new device known as Augma. Marketed as far safer, Augma becomes a hit, particularly thanks to its new VRMMO, Ordinal Scale.

It isn't long before Kirito and his friends find themselves immersed within this new game, pushing to reach the top of the rankings. However, there's more to the world of Ordinal Scale than any of them are prepared for. While Sword Art Online The Movie: Ordinal Scale isn't perfect, the increase in animation budget and focus on fight scenes makes it an enjoyable two-hour watch.

5 Sword Art Online: Alternative Gun Gale Online

A girl in a pink outfit rushes into battle with a pink gun in Sword Art Online: Alternative Gun Gale Online

Sword Art Online: Alternative Gun Gale Online is the only season that doesn’t have any of the main characters from SAO. Created by Kino no Tabi writer Keiichi Sigsawa, Sword Art Online Alternative is a spinoff series that features the game introduced in season 2, Gun Gale Online.

RELATED: 10 Anime That Got Too Popular For Their Own Good

Sword Art Online Alternative provided an interesting new perspective with its new main character and her story and motivations. It’s also fascinating to see a little girl decked out in all pink taking on big burly characters and, in a twisted way, the evolution and development of the main antagonist.

4 Sword Art Online The Movie Progressive: Scherzo Of The Deep Night

Asuna dashes forward with her sword extended in Sword Art Online: Progressive Scherzo of Deep Night

The Sword Art Online Progressive series of films continue with the second movie, Scherzo of the Deep Night. This second film takes place a few months into the players' time in Aincrad, as the players continue their trek to the top of the tower.

Since the point of Progressive is to cover the path up the tower in great detail, Scherzo only sees Kirito and Asuna reach the fifth floor. Fans who loved the first film will likely love this one as well, even if it's not as great a movie as the original. Being set within Aincrad is something of a cheat code, as all it takes is a great boss fight at the end to make everything worth it.

3 Season 3

Kirito and two friends pose with their swords drawn in Sword Art Online Season 3 Alicization

Released 4 years after the preceding season, Alicization was unexpected because of the time in between seasons. Season 3 introduced a new game and platform and felt like a completely different show from its preceding seasons. The story is nicely set up, featuring great world-building of the Underworld that goes in-depth with the human world and the Dark Territory.

RELATED: 20 Anime Endings That Ruined The Entire Series

Unlike prior seasons, the focus of this season is on the characters in Underworld rather than any of the actual players. Even Kirito, for much of the season, completely forgets he's not part of the world, operating the same as everyone else.

2 Sword Art Online The Movie: Progressive - Aria Of A Starless Night

Asuna dashing forward with a sword in the new SAO movie, Aria of a Starless Night

The Sword Art Online Progressive series is Reki Kawahara's way of showing he's still improving, and deserves a second chance. The light novel source materials involve basically Kawahara going back and detailing the entire journey, floor by floor. There's also a big change in that things are more focused on Asuna this time around.

Aria Of A Starless Night shows Asuna as a schoolgirl before getting pulled into trying Sword Art Online by a friend of hers from school. On her first day in the game, she gets trapped inside the game, and given the same ultimatum: clear all 100 floors to get out. Aria of a Starless Night is one of the best Sword Art Online projects, with beautiful animation, storytelling, and vocal performances.

1 Season 4

Kirito and his friends pose in armor and brandish swords in Sword Art Online Season 4

Season 4 is the most recent season of Sword Art Online, technically part 2 of Alicization. With the last season having a cliffhanger ending, season four immediately became one of the most highly anticipated series the season it released. In general, fans have reacted to it the best as well, making this potentially the most popular Reki Kawahara project yet.

The big change between last season and season four is the involvement of the “bad guys” from the dark territory. This season proves the antagonists aren't just the stereotypical villains looking for destruction. Each clan and race has their motivation for going to war, but aren’t necessarily evil. It might not be possible to top this season, even if it does feature Kirito at his most overpowered.

NEXT: 25 Most Popular Characters In Anime History (According To MyAnimeList)