Thanks, I’m going to give this a try.

Mirror’s Edge (2009 game, GOG version) is another game working out of the box. Looks like this one supports both DirectInput and XInput, and defaults to using DirectInput on my system.

Probably shortly after the 360 took off. So post 2005.

XInput was built specifically for the XBox controller, and does not support configurations with more buttons and/or axes than that has (I assume it can support devices with fewer inputs, but I'm not entirely certain). DirectInput, on the other hand, supported an arbitrary number of buttons and axes.

I think the reasoning was that having a fixed number of controls would be easier for game developers as they'd always know how many buttons and axes the controller has, as well as knowing which logical input is mapped to which physical button (provided the controller wasn't manufactured to completely broken specs).

I don't know what fighting sticks for XBox do with the analogue axes, I'd assume they claim to have them, but always at 0 (or 50, or whatever the default is).

Ori and the Blind Forest is another game where my controller works without any tweaking around needed, it makes me hopeful it could be the same for all Unity3D games.