It's a great show with great characters and a great story in each season. It's enjoyable for all ages, and has been part of my life since around 2013/2014. Rise of the Snakes (Season 1) and Legacy of the Green Ninja (Season 2) were two great seasons that served as a great introduction to the world of Ninjago.
Season 3 (Rebooted) was nice, and the technological beauty of New Ninjago City really added something to this season, that I feel has not been captured in any other season.
Season 4, The Tournament of Elements is my favorite season of all. It largely takes place outside of Ninjago City, and rather on Master Chen's island. At first I thought it really was just a tournament, but it was then revealed that Chen was stealing powers, which was a great concept. Skylor was a great side-character, and her redemption where she sided with Kai and the ninja after she betrayed Kai was great. The reveal that she was Chen's daughter was definitely unexpected.
Possession was another great season, and Moro was a cool villain. The preeminent was awesome, and it sort of meant the death of Sensei Garmadon, which was sad, and Nya as the water ninja was really cool.
Season 6 was the first time where I thought the ninja were completely done for, and I thought Nadakhan would prevail and destroy every last one of the ninja and their allies. Luckily, Jay and Nya made it to the end, and Jay used his final wish to turn back time and reverse all the events from season 6, AKA Skybound. Only Jay and Nya will ever remember these events, but it's still an important chapter for the ninja, especially Jay and Nya's relationship, and the true love that they share.
Season 7 could have been better, and is probably the worst of the original 7 seasons.
After Hands of Time, the designs changed. I was unsure of the new looks, but quickly warmed up to them. Seasons 8, 9 and 10 (Sons of Garmadon, Hunted and March of the Oni), are all part of the same story arc, the Sons of Garmadon, or the Emperor Garmadon story arc. It's a great story. Harumi and Mr. E are great, and Emperor Garmadon is too. Killow and Ultra Violet are cool, but could be better. The death of Harumi was upsetting. March of the Oni felt short, and it was. I wish the Oni got more time to shine as villains, and I wish the darkness would have slowly spread across Ninjago City over the course of the 4 episodes. I think it would have also been nice if they shined some more light on how the Oni were actually destroyed in the Tornado of Creation.
I'm still watching season 11, and haven't seen 12 or 13, so I will write a new review after having finished those. Goodbye!