Forgetting albeit the failed Frames Per Second of the PC version, I liked Arkham Knight. I thought it was well done, but the marketing for it and direction didn’t make it feel like one of the best sequels of all time: there was emphasis on the Batmobile. Not only was this a bad marketing idea, but it also put emphasis on an aspect of the game that was of lesser quality. Also, in terms of direction, it didn’t seem like adding upon the game as it could’ve.
Let’s look at the previous games:
Arkham Asylum takes place on Batman fighting the Joker, albeit Barbara Gordon as Oracle is with you.
Arkham City takes place in a city, albeit how big Arkham Asylum was sorta made it feel like it was the size of a city. Arkham City however is open world vs Arkham Asylum. Other characters in Batman Family/DC mythos show up as well.
Make Arkham City II/Arkham Knight/Arkham Asylum III/Arkham Gotham more open world. Have there be be robbers in every city harrassing citizens everywhere.
Have it take place in a larger place. This game was a port to the PS3 and Xbox 360, when it could’ve just been a current gen exclusive. The Arkham games and movie blockbusters generally expand larger.
Use a larger group of superheroes. This worked with the Lego Batman series. I’d be dying to see the use of the Outsiders, Nightwing’s Teen Titans or even the Justice League. Arkham City has you meet Azrael, play as Catwoman, etc.. Imagine Superman in an Arkham game for a certain portion of the game like with Catwoman. It had a very Heavy Rain-ish feel having the ability to play as multiple characters.
Have you choose which character you can play in the game opposed to just giving it one option during a certain section. This isn’t bad, but it seems like a good sequel version of the predecessor’s expansions.
Have Harley become the Joker’s Robin. I really liked the Harley design of being the runner of an Asylum at the beginning or Arkham I. I think that really fit her being a former psychoanalyst that falls in love with the Joker. It really could’ve expanded upon her characters in ways that have seen being introduced have been used for comic relief and fan service. That ending to Knight would have a good following as well.
More Bat vehicles, (and make them work!) Bat Boat. Bat Wing. Imagine Bat Wing battles opposed to Batmobile battles. Imagine Batman flying in the air with Superman and other characters.
Heck, make Arkham basically a GTA clone and have him ride any vehicle in the city: no pedestrian violence from him though please.
Give Batman more suits opposed to more items.
Now people may debate the technology isn’t there yet, but this is the same generation where we have large games such as Bethesda (albeit there are glitches!) and Xenoblade Chronicles X.
I could’ve also listed other stuff such as actually do Grant Morrison-ish Arkham stuff in it, which really would’ve been good, but this is a list of stuff I feel would be true to this franchise and brand.