The Revision 2026 demo party ended, and they've already released the videos. From the main demo competition, there is one long video, even with commentary. My two favourites are

Golden Egg by Gaspode - technically maybe not that challenging, but very nice composition and design

Razor1911 - Razor1911 - Depeche Mode casts a long shadow, but still a great demo

This is already a bit older, but I'm still amazed of how much is possible when using one of the state of the art engines (and lots of custom code, I suppose). But this is certainly nice eye-candy. Hopefully, the story and writing of the game will hold up the mark set by The Witcher 3.

The Witcher 4 - Gameplay UE 5.6 Tech Demo | State of Unreal 2025 - YouTube