Ahh ok, made some headway on this problem. Running ’emulation station’ returns this error:

/usr/bin/emulationstation: line 11: 2500 Illegal instruction $es_bin "$@"

I did some googling and it turns out that this error comes up if you’ve installed the RetroPie Raspberry Pi 2 image on a Raspberry Pi 1. I thought I had a Raspberry Pi 2 but I was mistaken: I have a Raspberry Pi B+ v1.2 (RPi1 basically), and I have the Retropie Raspberry Pi 2 image installed.

I’ll reinstall everything with the Retropie Raspberry Pi 1 image and see if it works.