Search YouTube for "Unreal" film previews. There are so many out there that were all realized with the Unreal engine. Maybe it's the algorithm, but all I see is stuff done in Unreal and I haven't seen anything done in Unity.
I searched for that and 'unreal engine film preview'. There were a few cinematics that have been made, but there was nothing that had to do with major vfx studios or even upcoming mainstream films.