A similar project is Ludo [1] which is part of the libretro family. More for emulation but really a clean UI (it actually has screenshots)
Back on topic, there's also Lakka as a LibreELEC with full Retroarch. I think there are other similar projects around, like EmulationStation.
I like the naked Retroarch UI so much better than emulation station so I thought that part was much better than retropie, but the amount of fiddling I had to do with the OS on a system that really didn't want me to do that ruined it for me.