OK Time to post a long one. So I kind of grew up with these games.
AC1: The concept was there, The story especially modern first civilization and apple thing was a good payoff at the ending. I didn't care much about Altair. It was 7/10 game at its time. And now it's just a boring chorathon that one should not play and just watch on youtube. It was a good game though. It's just that Ubisoft's open-world was really limited at this time. You couldn't even swim in the water.
AC2: Biggest improvement in any game ever. It featured three of the most beautiful cities in a beautiful time period. It started many long trends in franchises like recurring historical figures like Leonardo and base building. The story was awesome. The puzzles were awesome. The truth file was mind-blowing. And Ezio was Iconic. Gameplay-wise it doesn't stand the test of time though. My Favorite AC and the community's most beloved game. Ezio's Family theme is now the most iconic theme of the franchise, and of gaming history in general.
AC Brotherhood: Supremely refined AC with an OK story but awesome storytelling like Uncharted games. Absolutely loved being Badass in this game. The mission structure and flow were awesome. You could ride horses. And the multiplayer was lit. Was also one of the hard-earned platinum as it included online trophies. This could have been AC2: Blood and Wine though and this game started the yearly trend of incremental improvement rather than a build on top that AC2 was over AC1.
AC Revelations: The Atlair met Ezio moment is among the most iconic gaming moments to me. The engine started showing age. Apart from Ezio and the story, the gameplay started feeling redundant in this game. Master Assassin Yusuf was also very likable. You met Piri Reis. The setting looked great but there was a staleness on overall improvement. The revelation ending was awesome. It hyped ACIII heavily.
ACIII: The most disappointing AC. Connnor's voice was awesome, the story was cool but Haythem had more Charisma and stole every scene he was in. The gameplay was awful even though combat had some improvements. Looked horrible on consoles. The new engine was very unpolished. The main function of this engine was however fulfilled up to some degree in creating a wilderness. The ending was bad, real bad. They messed up. It was anticlimactic. Also, the setting was not that interesting to me personally.
ACIV: The engine got proper polish and it showed. The game looks beautiful. It is the last AC going back that stands the Test of Time to me in the gameplay department. Naval combat is awesome. It is the favorite AC of many people. The story was average. But Edward was awesome and the setting was awesome. If one does not likes Assassin's Creed games, they can still enjoy this game. Very Accessible game. A lot of fun. But this was the start of the downfall in the "Assassin" story and the main storyline. The start of modern trends like representation and stuff started. Freedom Cry DLC was made a full separate game later on this whole basis and AC: Liberation and other stuff. Legendary ships were legendary indeed, I mean El Impoluto was practically flying, the stuff of the legend I say.
AC Unity: Good Story. Best Gameplay for an Assassin Game but not as fun. Stunning Graphics. Intriguing Setting. You met Neapolitan. It had many technical issues. But overall a good game. Now people look at this through rosy glasses. The coop agenda was laregly unsuccesful. It represents the assassin's creed properly though. All sides of It. The Templars and the Assassins.
AC Syndicate: More boring story than this post. Absolute boring but the gameplay was fun. The setting was cool but the game had a really boring flow. Snoozefest storytelling after the very fast-paced first act. I actually liked Evie a lot. She was a good female protagonist without being tagged female protagonist, with proper attires and clothes and all along with a distinct personality.
AC Origins: Haven't Played fully. I actually guessed Bayak's motivation by simple deduction though. Huh, What has Ubisoft not killed yet in the AC games; a friend, a brother, a father, someone's wife, someone's sister, someone's uncle. Oh yeah, a child. Once they said the Protagonist is a fully grown middle age man I was like Bayak will lose a child isn't he.
AC Odyssey: Played roughly 400 hours in Pandemic times. Shill up summed it best. The story was really good and ended on a positive note depending upon your choice which was a fresh thing to see in an AC game. The endgame was awesome. Playing as Cassandra is a horrible choice. I played as Alexios and Cassandra both for 200 hours. There is a vocal minority who puts Cassandra at a pedestal because Ubisoft with their many fake proxy accounts tried to peddle female protagonist narrative for brownie points. Cassandra as Deimos was awesome. That went much better with the narrative. The game was although very very much stretched. I enjoyed it but don't want more of the new formula.
AC Valhalla: Haven't played in full. I dredd it. I don't care about AC anymore.