For me Genshin Impact and Hades (including Hades II) are two examples. These games have relatively simple art styles in comparison to e.g. the realistically painted art of certain Blizzard games (WoW, Hearthstone hero portraits), but they are hard to learn even to someone more advanced in art creation.
Devil Daggers
The sheer amount of attention to details that the game has is just pure insanity The game has special sound effect that plays, to let you know that the flying homing skulls are literally right behind you, just so that you don’t have to look behind you all the time to know if they’re near or not The complete lack of a user interface yet the game still communicates extremely well how everything works by just… throwing it at you and letting you experiment