Personally, if I could only get two figures per game, they would be:
Arkham Asylum:
-Batman
-Joker
Arkham City:
-Batman
-Mr. Freeze
Arkham Knight:
-Batman
-The Scarecrow
The Arkham Knight is a cool looking character, and I want the figure, but he's nowhere near as compelling as I'd hoped he'd be. The Jason reveal seemed forced and out of nowhere ("secret wing of Arkham?" Huh?"). Plus, it's one of those weird situations where I'd be lying if I said my own personal head canon wasn't superior in every way. Young Adult Damian, now the leader of the League of Assassins, in the wake of his mother and grandfather's passing, decides he'll bring the League into the 21st Century with superior military technology, and, basically, an understanding of all of Batman's tricks and how to combat them. The Arkham Knight moniker would've made total sense as a way to memorialize those he'd lost in Arkham City, all the while taunting Batman and pushing him to figure out why he's doing what he's doing, and becoming even more and more unstable, as Batman's inability to figure it out consistently angers him.
Plus, the reveal would've been so much more compelling. If he's unmasked and it's simultaneously a gut punch reveal to Batman that he has a kid after that "night in Metropolis," and that said kid hates his guts, thinks he's a murderer who killed his grandfather, and is a failure who didn't save his mother? Just imagine Batman, surrounded by TV screens airing news coverage of him carrying The Joker out of Arkham City, with Damian berating him and asking why he felt so sentimental about his greatest enemy, who murdered his greatest love (in Damian's eyes), while leaving her to rot in the ruins of Arkham City.
But yeah, Arkham Knight. He was okay, but, easily, the best part of AK was the Scarecrow. In terms of character design, the performance by John Noble, and the fact that HE ****ING WON, I feel like, if they're going to continue this line, Scarecrow needs his due.