About to start Hearts of Stone and Blood and Wine from The Witcher 3. I was wondering is there any expansion/DLC that beats these cause I can't think of any. The ones that come to the top of my head are so far behind these masterpieces. 

Oh man several immediately come to mind

Warcraft 3 - Frozen Throne
StarCraft - Brood War
Cyberpunk 2077 - Phantom Liberty
Destiny - The Taken King
World of Warcraft - Wrath of the Lich King
Elder Scrolls 4 Oblivion - Shivering Isles

Don't know if that's the exact placements I would put them, but they're definitely among the best

I just realized I probably haven't played a ton of expansions, but some of the good ones include:

• Commmand & Conquer: Red Alert 2 - Yuri's Revenge
• Grim Dawn - Ashes of Malmouth and Forgotten Gods (Fangs of Asterkarn falls short of both of them so far, expect for great endgame additions)
• Titan Quest - Immortal Throne

Some Total War games also have some well-reputed expansions, I believe, e.g. Fall of the Samurai for Shogun 2.

Many of the Truck Simulator map expansions are also considered quite good. They're not my favourite kind of a game, but I've had some fun with ETS2, including some nice map expansions.

Do standalone expansions count? Crysis: Warhead was really good for the most part.