In FFXV the music is great. Graphics are OK. The story is not well told. The pacing is shit. The world feels empty, you expect to meet many people and visit many cities in a Final Fantasy? Not here.
It is... I don't know. I played it when it was released and for me it was a disappointment. But it has some good points.
Regarding the battle system I guess it is OK, but not my cup of tea. Gameplay-wise again it is OK. The characters are insufferable. Most sidequests are a lifeless repeat of each other, the typical kill X monsters of type Y stuff.
It depends what do you mean by all that. If you mean feeling like a great final fantasy with great characters and music, an interesting story and a feeling that the world is not empty then the best ones are FFVI and FFIX.
If you mean a great open world RPG with nice gameplay and graphics where the side quests don't feel like a lifeless repeat then Witcher 3 is a good example.