@mitu Thanks for confirming that.

In the meantime, I was able to determine that my HDMI monitor also has a 3.5 mm jack that I never noticed before, so I can plug my headphones into that instead.

Assuming you are using the latest version of Retropie, you did not mention your build other than a wired 360 controller. You should read this: https://retropie.org.uk/forum/topic/3/read-this-first Then the following:

If you had your controller plugged in when you booted up it should have asked you about controller configuration. If so, this tells you everything you need to know about configuring a controller. Follow these and you'll be gaming in no time.

https://github.com/RetroPie/RetroPie-Setup/wiki/RetroArch-Configuration
https://github.com/RetroPie/RetroPie-Setup/wiki/Controller-Configuration

There's no need to create a new post ever time one of your former posts isn't answered. It should work with xpad out of the box unless it's some janky controller or an insufficient power supply or some other thing. But since you didn't provide the details requested on the read me first page it's hard to help you.

I finally got this to work. The key was installing both xboxdrvr and xpad. I also copied the working xbox 360 controller config from the wiki (here) and restarted the computer. After that, all the controls started working except for the d-pad. I had to go into the retroarch RGUI menu (the keyboard was also working now, so I had to use it to navigate the menu since the d-pad wasn't working) and adjust the controls for the d-pad in all the emulators. For some reason, it was the only part that wasn't working. I did notice that my triggers are handled differently for the two types of controllers. The 360 controller the triggers act as axis while the rock candy one is treated as buttons. This changed the axis that are used for the d-pad (which might also be weird. I would have expected the d-pad to be buttons, but that's no the case).

At any rate , I finally got this working. Hope this helps if someone else is having similar issues.