Shin Megami Tensei III: Nocturne already felt like a throwback of a game back in 2004. At a time when JRPGs were continuing their evolution into full-bore cinematic experiences, Nocturne is a bizarre dungeon crawler from an older school.
It's tempting to draw comparisons to Pokémon, since you spend a lot of Nocturne capturing and micro-managing your personal squad of monsters, but Nocturne really is its own thing. It combines traditional JRPG mechanics with a high difficulty curve and a dark storyline, and the result is still remarkably unique 17 years later.
I'd argue it's an acquired taste. In a genre that's usually known for black-and-white morality and simple stories, Nocturne sets up some dark, Gnostic moral and ethical clashes. It's basically a 50-hour philosophy thesis with a lot of punching demons.