Okie-dokes, I finished both Avatar: The Last Airbender and The Legend of Korra, but I don't feel like splitting this post between the TV thread and this one so I'll discuss both of them here. I didn't read through this thread so if I write something here you disagree with, it's nothing personal. I'm also forgoing spoiler tags.
Avatar: The Last Airbender
I think collectively it's the better of the two though I still feel like they're really difficult to compare which I'll get to later. In the first season, it was pretty clear that the writers had a story arc in mind. Aang had until the next summer to defeat Fire Lord Ozai before Sozin's Comet passes close enough to Earth for the Fire Nation to **** things up. It was appropriately three seasons long and even then, there were a few filler episodes that could have been cut or the one or two important bits could have been combined into other episodes. Still, having a set arc and knowing where to take these characters made the show feel more cohesive as opposed to each season being a separate arc like The Legend of Korra.
Book One: Water is probably the weakest season, but I don't want to be too hard on it. They have to introduce the characters and the world, and naturally that takes time. There's no way around that. Origin stories are a necessary evil. It's difficult to make exposition interesting.
Book Two: Earth was easily the best season across both shows. It isn't even that close either. Besides being able to jump right into the story, Toph Motherfucking Beifong was introduced. She was by far the best character in either show. She made every scene that much better by being in it. I liked the show enough before Toph showed up, but her character is so excellent that I had trouble not watching the next episode. I liked the other characters too (probably Aang the least); they just aren't as awesome as Toph.
Additionally, Azula was a better season villain than Zuko, partly because I expected him to end up being good which totally happened. The writers weren't really shy about hinting at it either. The trajectory of Azula's character was harder to predict and the show benefited from that. I didn't really buy her descent into complete psychosis by the end. It happened too fast. She seemed more sociopathic than full-on crazy.
If I didn't already know there was a third season, I probably would have been more surprised by the complete Empire Strikes Back-esque season finale with the good guys losing. Still, that was such an awesome finale to a really strong season. The weak link was probably the three or four episodes Appa was kidnapped and Aang kind of broke character. I get being upset, but he became downright belligerent and annoying. It's forgivable because something something Toph something.
Book Three: Fire started very slowly. There was a lot of filler at the beginning of that season. That beach episode was particularly weak. There were some funny moments and minor character stuff (albeit involving characters who aren't that important, Ty Lee and Mai). Besides the Combustion Man part, it's mostly filler. The bloodbending episode was cool, but there was no payoff for it. Katara almost bloodbends the man who killed her and Sokka's mother then just walks away. I understand the importance of Katara choosing not to kill someone, but she didn't need to learn an entire advanced skill of waterbending to get to that point. It just seemed like the writers needed to pad the season because they didn't have enough story for a full 20-something episode season. It was a good episode, just kind of pointless in the grand scheme of the show.
The season picks up considerably when Team Avatar fails again during the solar eclipse. Obviously, they were going to fail (since it was in the middle of the last season), but that was a major turning point where they got rolling towards the finale. It was a very strong ending and the fight between Aang and Ozai did not disappoint. My only issues with the finale are the previously mentioned Azula craziness and the Deus Ex Machina moment when the Lion Turtle gives Aang energybending so he doesn't have to kill Ozai since this is a kids show. Not that I expected a brutal murder scene, but Deus Ex Machina is cheating and cheap storytelling. I understand why the writers had to do it; I still didn't like it.
Ultimately, Avatar: The Last Airbender is a good show. I thoroughly enjoyed it, certainly a lot more than I thought I would. When the show premiered, I was already out of my anime phase and I had already given up on television a year or two before. Avatar: The Last Airbender seemed like another American show that was trying to cash-in on the anime craze, and I didn't care enough to give it a chance. I'm glad I finally did though binge-watching certainly makes it easier to get hooked on shows. The animation wasn't great in the first season but improves in each subsequent season. The series finale was just so amazingly well-done. Still, the animation in The Legend of Korra trumps it entirely.
And it's a shame that Nickelodeon didn't greenlight the follow-up story about Zuko and Azula's mother as a movie. It would have made a good epilogue. I just read the summary of the graphic novels.
The Legend of Korra
It's a very different kind of show than its predecessor so it feels like the only reason to compare the two is because they take place in the same universe. However, everything is different: tone, style, storytelling etc. Even though the writers generally do a pretty good job of connecting the seasons, they can stand alone with story arcs that resolve themselves at the end of each season. Korra's character arc continues from season to season as well as some of the other characters though most of the other characters don't have enough depth to matter.
I think Oblivion mentioned in the TV show thread that The Legend of Korra was only supposed to be a 12-episode mini-series. I'm really glad Nickelodeon decided to expand on it because Book One: Air was pretty mediocre though Nickelodeon's meddling is probably the reason why the shows suffers in certain places. They had to do another whole origin and introduce brand new characters (which collectively were immensely worse and uneven than Avatar: The Last Airbender's cast). Then, there were whole episodes devoted almost entirely to Avatar Quidditch (or pro-bending, who cares?). The rapid advancement of technology in the 70 years between Avatar: The Last Airbender and The Legend of Korra take place seemed absurd to me. It's fiction so I tried to ignore it.
Amon wasn't even that interesting, and it wasn't surprising at all that he was a bender though I suppose this was the ultimate payoff to that bloodbending episode in Avatar: The Last Airbender. If I take it that way, it still plays out more as something the writers tried to justify than something that was planned all along. It seemed a little lazy that people can now bloodbend any time (not just during a full moon) and that Amon can use it to take away someone's bending ability. It was such an exclusive ability in terms of knowledge and availability then the writer's were like, "Ahh, **** it." Giving Korra the ability to restore people's bending ability (especially after regaining bending herself) was a cop-out. In retrospect, it makes Amon a far less threatening villain. I wonder if the writers would have just left Korra without most of her Avatar powers if the show remained 12 episodes only. That seems like a pretty finite way to end things. The next Avatar in the line would presumably be able to master all the elements again.
Book Two: Spirits was much better even if it felt disconnected from the first season. There's greater weight to the events in subsequent seasons because one leads into and is directly responsible for the next. Korra leaves the spirit portals open which gives people airbending including Zaheer who uses it break out of prison. Zaheer kills The Earth Queen which fractures the Earth Kingdom and throws the entire region into chaos. He also poisons Korra which leads to Kuvira uniting the kingdom instead of Korra.
Anyway, I wasn't especially impressed by season two until the Avatar Wan episodes (I really liked the art style too). Unalaq wasn't a very good villain, but Vaatu changed the stakes. Still, defeating Vaatu caused a problem for the rest of the series. Once Korra purifies the spirit of chaos and darkness, I had trouble believing other villains could pose a real threat.
And good job casting Aubrey Plaza as Eska. Kudos to whoever made that call.
Book Three: Change was probably my favorite season of The Legend of Korra. It had the best fighting and the most consistent storytelling in the series. The Red Lotus were the best villains since Azula, and they were all written and portrayed fairly well. Still, there's a bit of cheating at the end. How do you get around the fact that Korra defeated the greatest threat to the world and the Avatar line (that also cut her attachment to her previous lives)? You literally handcuff her. Then, you poison her. The whole history with Raava and Vaatu raised the stakes of that battle and made it far more interesting. There's really no where to go but down after that.
I thought Korra was going to end up fighting all four main members of the Red Lotus at the same time and maybe that would even the playing field. Still, Korra vs. The Red Lotus/Zaheer was just immensely enjoyable and collectively my favorite fight of either series, even with Korra de-powered to make the fight close. Additionally, it was nice that the writers clarified that airbending has an advanced skill (flying). It was one of those things that I was left wondering about at the end of Avatar: The Last Airbender. Lightning didn't really make sense for fire, but fine. Earthbending has two advanced skills: metalbending and lavabending. Waterbending has bloodbending though if waterbenders can control any form of water, shouldn't that also include air?
Book Four: Balance was considerably weaker than the previous two seasons, but still stronger than the first season. Kuvira wasn't a very good villain either though Zelda Williams did her best. She had a certain presence to her; she just didn't have the power to back it up. Again, they cheated by handicapping Korra. The only reason Kuvira wasn't defeated immediately was because Korra was still dealing with the residual effects of the poison from the previous season (and the little bit still left in her body). It's weird that many of the major villains across both shows just end up in prison. Ozai, Azula, Zaheer, and (presumably) Kuvira are jailed despite some pretty terrible crimes. I expected Kuvira to be thrown into the Fog of Lost Souls (which I suppose is just another kind of prison albeit an extremely awful one) after a short fight in the Spirit World considering her crimes include kidnapping, treason, torture, slavery, and attempted genocide.
I didn't really like the ending; it felt rushed. The fight ends, Korra and Kuvira talk in the Spirit World, then there's a wedding. I didn't really care for the pairing of Korra and Asami. I'm NOT against it (EDIT: I really mean I'm not against it. Jebus.). However, I didn't think the writers established enough between the two to justify it. I realize that this is a Nickelodeon show and there's a limit to what they're allowing the producers to show, but if they're going to do it, then commit to it. Leaving their relationship ambiguous is a disservice to the message they're trying to make. Still, I just didn't particularly like any of the love story stuff in either show. It generally felt forced, distracting, and unnecessary.
Ultimately, they were both good albeit flawed shows. I'd have to watch them again, but I definitely noticed some plot holes and inconsistencies. I think the shows definitely suffered by being on Nickelodeon as there were things that were either glossed over or ignored. Still, they got away with a lot for a show rated Y7.
And I didn't want to put this next bit in the middle of my (already very long) write up. Meelo was so fucking annoying and terrible. I generally like kids; I just hate kids like Meelo. He wrecked every scene he was in. He almost ruined the episode where Toph returns since he was featured so prominently. He's the anti-Toph. Everything that made Toph awesome and fun, Meelo was the opposite of that. His voice, his lines, his mannerisms, his personality, his design, his everything was awful, flat-out fucking awful. And he never did anything that important to justify his existence. Anything he did could have been re-written for Jinora and/or Ikki. He's such a horrible choice by writers, directors, and showrunners who have done a mostly good job that I'm docking points from The Legend of Korra just because Meelo is that bad. And fartbending? Fucking seriously? Goddammit.
Still good all-around shows. I recommend them.