Surprisingly enough I noticed there was not a general suggestion thread for retrocopy, so I decided to start one, with some suggestions for retrocopy of my own.
These may be things you are already implementing, RetroRaplh, but for savestates it would be nice if there was a "sate saved" message, as well as state loaded.
As for input, it would great if at least there was a note of what every button does, I noticed F5 and F6 cgange screen filters, which mess with my savestate keys. I think it would be more convenient if all the directions and maybe a few buttons were made "universal" for systems, so I wouldn't have to configure all the directions when they're the same since they're all on the same gamepad. I would suggest making it toggleable though, since I sometimes want to switch to my genesis pad for genesis games using my adapter. Also, could you allow the fastfoward/rewind graphic to be disabled, a la NesDS?