Lots of bad suggestions. Dragon Quest XI is a good game, with an acceptable difficulty if you play it with Stonger Monsters but it has a lot of the negatives of modern RPG's such as total linearity, there's *always* an NPC nearby telling you exactly what to do, a lot of cutscenes, the quests are boring, and you can make the argument it's exhaustingly long with part 3 being abysmally bad with aggravating fights, and rewriting 100 hours worth of story and character development for no real reason.
Go with Romancing SaGa 3, it's traditional in the jRPG sense to be a good intro to the genre, but has enough of Kawazu's love of tabletop to be a hit with a cRPG fan - you're given the opportunity to choose 1 of 6 protagonists all in different starting areas, with different starting abilities, gear, and aptitudes. Some characters have unique characteristics, such as Mikhail's War Games, or Khalid's greed and an inability to turn down the monetary reward for quests. Stats are fixed much like D&D except for small boosts from gear, which determines a character's usefulness with magic and weapons. There are over 20 recruitable characters in the world, some being unrecruitable based on your chosen protagonist. A bunch of side quests for you to do, some with major impacts on the world depending on the sequence of events. Oh, and the thrill of sparking a new art that changes the flow of battle can't be beaten by any other game.
SaGa: Scarlet Grace is similarly awesome in all regards to RS3, but has a lot of obtuse mechanics, with a daunting number of characters (>50) with a very complex combat system that can be off putting and oppressively difficult until it suddenly clicks with you.