I noticed that the R Pi 2 port of Libretro Mednafen PCE Fast does not support .iso extensions even though these run on RetroArch on other platforms (tested Wii and Windows versions with same disc image). A lot of my PC Engine Super CD games are in this format, is it possible to play them on the R Pi 2?
I am using .cue/.iso roms in mednafen-pce.
Make sure you have the syscard3.pce in your BIOS folder. Then check your es_systems.cfg (probably in /etc/emulationstation) to see if your entry for the pc engine has .iso added to the supported file endings. Also if you are using .cue files check if the filename of the .iso file is the same name as the one written down in your cuefile. (it’s case sensitive)