This is just between these two games, Ni No Kuni vs FFXIII. Please refrain from using your adult dictionary as I know a verbal war breaks out between fanboys and haters whenever FFXIII is mention. Now lets discuss.
Ni No Kuni, its got everything that was left out of FFXIII. T0wnz, a world map, ships, npcs and even side quests that doesn't involve just hunting monsters. I felt FFXIII was lacking in all those aspects and more so when you force people to play through a 20+ hour tutorial along a narrow corridor. FFXIII's battle system, crystarium leveling system, and even the job class paradigm shifts weren't up to snuff. Don't even get me started on the characters.
"Tetris: that rampant sexual symbolism, inserting a piece into a slot repeatedly, is downright vulgar. Game needs an AO rating." LGCulgan
Both are (or appear to be) decent RPG's. I personally got turned off to Ni No Kuni as a game, when I played the demo, but that's just me. From what I could tell, it is a decent game that I likely would have enjoyed fifteen years ago, but I just could not get past the "monsters fight for you" type of combat that the demo indicated the game to be.
Obviously, they are not the same type of RPG. But then, Ultima and Might and Magic were not the same types of RPG either.