[fxtentacle]

If you can read C++, this one is surprisingly easy to get into. You can do most things with the amazing graphical editor and for the very few cases where that isn't powerful enough, you can debug the whole thing in Visual Studio which means you can see parameters and stack traces for everything. And in my personal opinion, classes are predictably named and layered in an useful way.

I found learning it and working with it quite enjoyable, especially compared to my experience with Unity where the lack of source code forced some very ugly workarounds on us. And with "only" low millions in annual revenue, Unity wasn't even willing to discuss the price for source code access... but with UE, you get a triple A game as demo project for free.