Part of the continuing split of Unity indie and UE4 'AA/AAA' is less to do with the capabilities of each engine and more to do with who has the longest experience with each. They both are creeping in on one anothers turf in that respect.
Cities Skylines?
I know, I know, Correlation does not imply causation. But just from wikipedia:
> On March 19, 2014, at the Game Developers Conference, Epic Games released Unreal Engine 4, and all of its tools, features and complete C++ source code, to the development community through a new subscription model.
Same year Unity took best engine.
> In July 2014, Unity won the "Best Engine" award at the UK's annual Develop Industry Excellence Awards.[1]
Unity made Epic react.
[0]: https://en.wikipedia.org/wiki/Unreal_Engine#Unreal_Engine_4 [1]: https://en.wikipedia.org/wiki/Unity_(game_engine)#History
Epic's AAA market ended up with bigger budgets and a demand for more control, so many of them simply created their own engines. So most UE games seem to be big budget indie titles (Obduction, PUBG, Psychonauts 2) or tight budget AAA titles (Street Fighter V, Shenmue III)