My thoughts on the series:
Assassin's Creed
This has not aged well. The series has come a long way since. The game mainly consists of repeating the same activities - street assassinations, flag collecting, eavesdropping, pickpocketing - across city environments. You don't have to do all the activities, just a few, to access the main story missions in each chapter. These tend to be ok but are simplistic compared to how they developed for the rest of the series.
Some of the areas, like Masyaf, still look good if you use the overhaul mod. Make sure you use PCGamingWiki for tweaks. The game looks horrible unless you put the multisampling on max (3 in the config file). Other areas like Acre and Jerusalem look drab, grey, boring.
The parkour gameplay is frustratingly inaccurate. Many walls which look climbable can't be climbed, or have an obstacle half way up which looks like you should be able to get around it, but can't. Often you'll be stood at the top of a wall or a tower and press the jump button towards something else and you jump in completely the opposite direction. This makes some sensitive sequences like chases an utter nightmare. We've been spoiled by games like Uncharted which do it so much more fluidly, but that has come with time.
Play if you're interested in the Crusades setting.
The other day I installed vanilla ass creed 1, and I felt that graphics and animation much more believable than the sequels. It was kind of "realistic". From AC 3 and beyond, the characters are like Spiderman, doing super jumps that defies gravity. Also, the drab look does feel atmospheric. The game felt less silly compared to the other installments. But it really is boring and repetitive. Every kind of mission is the same thing in every city: pickpocketing, eavesdropping, beat up, etc... were missions available to get info on the "boss" targets, and for each boss, they would all play the same way. No variations. Also, beyond the cities, there was a big open wild area that was very cool, but there was nothing to do on it, other than find collectibles.
A much bigger emphasis on story this time around, with a much more likeable protagonist. Most of the boring side activities have become optional. The parkour works better and you can do more kinds of assassination like aerial assassinations, allowing for more varied gameplay. There are some spectacular setpieces. The soundtrack is outstanding. The Codex soundtrack thread is littered with examples of Jesper Kyd's work on this game. The modern day storyline is also a lot better and there's a little bit of town management as Ezio builds up his family's stronghold.
Play it - it's one of the best AC games.
It's when they applied the GTA philosophy: all missions are "story" related, and there's some repetitive filler mini game type missions, but they all have a better integration to the main story. So it's like a GTA without cars. If one likes GTA for it's storylines and not because of silly dumb killings, you'll probably enjoy it. Also, aerial assassinations were present in the first game. What is new is the fact that you have new moves, like killing two guys at the same time and double aerial kills. And ezio can learn hot to climb higher.
Assassin's Creed Brotherhood
Direct sequel to AC2, it expands on the town management of the first game to allow you to buy up and develop all of Rome. The soundtrack, again, is outstanding. Systems from AC2 have been built upon and refined. Animations are better, even more ways to assassinate people, and there's a great brotherhood mechanic where you hire and develop your assassins - all the best AC games have copied this since.
Play it - it's one of the best AC games.
it's as good as AC2. It made things easier with the aid of brotherhood allies, and chain kills. Ezio is unstoppable. This is the game that they added side optional bonus objectives in every mission, like kill everybody undetected, o kill in a specific way, or complete the mission without fallin in the water, which was really challenging sometimes. every mission had 2 side objectives. This is kept for the whole series from this game on. also, this game introduces a cellphone minigame where you send your assassin's on missions around europe so you get money and improve their abilities. they could die in these missions, but there was a percentage of success before sending then on missions.
Assassin's Creed Revelations
I didn't enjoy this one as much as it felt a bit pointless. Ezio's story seemed kinda done with AC:B but they found a way to keep it going, only with him now as an old man trying to find love. It's set in Constantinople, and there are flashback sequences with Altair, so it feels like a mix of AC and AC2. Not much else to be said. I don't remember it that much compared to the other games.
Play it if you're a fan of the previous games.
It's the best looking game of the old engine, but it's a short game and feels more like an expansion. Ezio has now a hook that can be used in parkour and combat, there's a tower defense minigame. Every new addition to gameplay in the series is kept for the follow up sequels until now. Storywise, it ends the ezio/altair storyline in a way that was completely unnecessary to have a sequel, except there was that shitty present timeline.
Also, about this old engine, the cities felt more lively in a GTA sense, better that when they changed to the AC3 engine.
Haytham Kenway is one of the best characters in the series - and a lot of the game still looks good today, especially the wilderness sections. Some parts of the story are good even though it portrays a one-sided view of the American Revolution (rebels good, British bad). The modern day storyline gets more attention too.
Assassin's Creed III introduced the ship mechanic which was built upon and refined in AC IV and Rogue.
Play it if you're a fan of the previous games.
the redeeming factor of this game is the introduction of naval battles which, though very arcade-ish, they were really fun. Also, they sold the game with picture a a protagonist that you only get to play with only in the second half of the game, making the whole beggining feeling like a huge prologue. Then, when you get to play the indian guy, you realize that the prologue guy is much more fun to play with. The game also brings back the "wilderness area" like the one in AC 1. But old USA setting is boring.
Assassin's Creed III: Liberation
A PC port of a PS Vita title. Set in New Orleans around the same time that all the AC3 stuff is kicking off.
Play it if you're a fan of the previous games.
It's simpler, but yet introduces the disguise/persona feature gameplay. but its also very simple and actually cumbersome.
Assassin's Creed IV: Black Flag
The game is outstanding. Missions have optional side objectives which increase the difficulty somewhat. There's a huge continuous, open world to explore by ship and by land, and doing the random shit now actually help you upgrade your character and your ship, the ship battles are excellent, the soundtrack is pretty good (although still not a patch on Jesper Kyd's work on AC 2). Edward Kenway is a pretty interesting character. The modern day stuff gets a bit shit, unfortunately. But everything else works so well, and with a high degree of polish, and doesn't seem to have aged at all.
Play it - it is probably the best AC game.
It's as silly as every AC game, but it is really fun, and I guess it was made because many people considered AC3 a huge disappointment, but everybody praised the ship missions in that game, that they run to make an entire game based on that feature. It still has on foot sequences, but the fact that they made it shorter made the game fresh.
The optional side objectives are present since brotherhood.
Assassin's Creed IV: Freedom Cry
A standalone expansion to AC IV which expands on the character of your first mate. He goes around killing bad guys with a machete, freeing slaves, and building up his own ship. You spend a lot more time on the ship with this one, so play it if you like AC IV.
very short
Mechanically the same game as AC IV, with the open world and ship gameplay that made that game so fucking great, but the setting is more akin to AC 3. What I love about Rogue is you finally get to play as a good guy - a templar, basically, who's more or less aligned to the British cause. You see why he thinks that way - he has valid reasons for seeing the assassins as scumbags. Would have liked to see this developed more in the series. Still holding out hope for a sequel of some kind.
Play it - it's one of the best AC games.
More of AC IV, and you play with a guy who sides with the templar guys.
Technical issues prevented me from playing it.
Horrible, more repetitive than AC 1. The worst AC game. Everyday is revolution day: they made crowds revolting in front of Notre dame, and from Arno's youth till the end of the game, which is years later, there was always that riot in front of notre dame. Also, in many other places/squares. The city is very beautifully remade though. The fact that there's no eiffel tower at the game time line made the devs create a bleeding effect in which present guy experience glitches in the animus that would merge othe memories/timelines, making you appear in the belle epoque or world war 2, so you can widen the scope of virtual Paris tourism. But the game is a shore.
Oh, multiplayer was integrated in the main game, so you could play mission's in co-op, but the novelty wears of after playing a couple of times.
Assassin's Creed: Syndicate
Technical issues and the fact that my CPU isn't up to par have prevented me from playing it.
Silly, but an improvement on unity, but it reached a point when the series is mostly bad by now. It's mostly a forgettable game, but some fun can be achieved from it. It feels like the devs noticed the series was stagnant and unity was shit, that you can see the effort they made to change it into a better game. It's also the 1st time an AC game doesn't take itself too seriously. It's now closer to GTA since you have chariots on streets that you can rob. Combat is more akin to batman games, and better than the whole series combat.
My favourites in order of preference:
Rogue > IV > Freedom Cry > Brotherhood > II > III > Liberation > Revelations > I
Mine:
Brotherhood > IV(freedom cry is part of it) > II > Rogue > III > Revelations > Syndicate > I > liberation > Unity
In any case, I like AC games overall, because I like my open world GTA style games. I know they're popamole, I know they're silly. But I can get some enjoyment from it.