I recently replayed the Arkham series, starting from Origins through Arkham Knight.
Those are great games with top notch graphics, good story, excellent characters and atmosphere, decent change of pace between stealth, exploration, investigation and original combat.
But when it comes to side content and boss fights, no, I am sorry, the Arkham series is as lackluster, if not worse, as Insomniac's Spider-Man.
Arkham Origins: it has the best boss fights in the series and the side content leading to Anarky is great. All the rest is forgettable. Bird was bad and bugged.
Lady Shiva is a great character, totally wasted both in the main game and in the prequel DLC. She never felt menacing and in both boss fights with her she needed ninja goons.
Deathstroke is the best boss fight in the series and maybe of all superhero games, Firefly a close second or third to Mr. Freeze.
About Mr. Freeze, his boss battle in the "Cold, cold heart" DLC is a copy-paste from Arkham City.
Copperhead was just QTE and reflex training. Bane and Joker were just smash "square to win". Deadshot was good too, but didn't feel scary at all.
Killer Croc was so easy that I would call it "end of tutorial".
Arkham Asylum: in the game there are just two real boss fights, the one with Poison Ivy which is "rinse and repeat" a lá Crash Bandicoot and the final fight with Joker, which was silly to say the least. Victor Szasz was a two times takedown using a single gadget.
Killer Croc was just a puzzle, walk there, run in that direction, etc.
The Scarecrow level was great the first time, but the idea has been abused two other times plus DLCs. Honestly, I would like it better as a one hit wonder, rather than repeating always the same good shit.
Harley Quinn was just a cutscene.
Bane was a joke, he is like the smartest foe of Batman, but he behaves dumb all the time. His character design was worse than Origins, it didn't help either. Also, the fact that many goons have his moves and skills in the second part of the story takes away from him a lot.
Arkham City: I am outraged for the treatment that Penguin, Two Faces and Deadshot get in the game. Not only their character dedign got worse from Origins, but also their screen time is too short to be impactful in any way.
The investigation leading to Deadshot was bad and glitchy and took too long, imo. His fight is just a single button takedown. He is my favourite Batman villain, so you get the outrage I feel.
Another thing that outraged me were the Szasz and Hush side missions. Szasz, once again, is defeated with a single gadget/takedown, Hush is never faced, he is just a cutscene. I liked the teaser for the sequel, but damn! He too is just a cutscene in Arkham Knight!
The Solomon Grundy fight was simply bad, I mean why do I have to hit those spots in the ground? He is basically Zombie Hulk, he is strong, but stupid. Let me fight him with my brain, not with Crash Bandicoot patterns. Make my hits be felt as ineffective against him.
The Mad Hatter was another good meta-level like the Scarecrow ones in Asylum, I loved it, nothing bad to say about it, heck, they even used it just once, instead of repeating it over and over like Asylum did.
The fights with Clayface and Ras'Al Ghoul would have been better without goons supporting it; plus, a good one on one fight between Batman and Ras, without special effects and silly tricks would have worked better.
The boss battle with Mr.Freeze is so good that I cannot say anything bad about it.
There isn't a single good boss battle in Arkham Knight, Imo and the side content is so repetitive and redudant that all in all I wouldn't use the Arkham series as pinnacle of boss fights and side content.
Both Scarecrow and Arkham Knight/Red Hood were a huge let down...
Tl;dr= Spider-man side content and boss battles might not be the best, but Arkham series isn't any good either.