Before Rocksteady sent their Batman off with a bang in Batman: Arkham Knight, WB Montreal was tasked to make a game to keep the Arkham franchise on its bi-yearly release schedule. The result was an underrated prequel to the franchise, titled Batman: Arkham Origins.
Focused on the Caped Crusader's early years, this title is all about a young and slightly inexperienced Batman coming to grips with his responsibilities as Gotham's savior, learning to trust others, and meeting his arch-enemy, The Joker, for the first time.
Arkham Origins has some of the best Batman and Joker moments in the series (aided by the excellent voice over work of Roger Craig Smith and Troy Baker). On top of that, it also has the same excellent combat and stealth sequences from earlier games in the series, and it also has some of the best boss battles of any game in the franchise.
It's not perfect, of course. There are plenty of technical issues that were never fixed by the developer (because clearly DLC is more important than the actual game it's for), and it doesn't push the series forward in any monumental ways, but it's still an exceptional game that fans of Batman should give a shot.