I have the exact same problem with mine, I’ve only really had a quick chance to set it up. What exactly did you do to show the rest? I’m a complete newbie to all raspberry pi so I’m not 100% sure on everything. Thanks
if you put in a usb memory stick retropie will make a folder called “roms” that will have folders inside for all emulators, all you do is pull it out, hook it up to your pc and ad your rom files in the correct folder and re-insert it into the Pi, it will take a while depending on how many roms you added then restart your Pi and the ones that are compatible will show up, if you do not add any roms to an emulator it will not show up.