@mitu I was just messing around with all of this. I don't have a RP4 yet, but plan to get one. I just wanted to get familiar with the different gaming-centric OSes before I got mine. I'm running this on a laptop that's running Windows 10. I need the ability to have Windows 10 running while I play around with this RP and emu stuff for the time-being. Using VirtualBox gives me that ability. I checked the '3D Acceleration' checkbox and now RetroPie runs. However it's really slow and beyond the configuration menu, I don't see anything else. I've got a VM that only loads an SD card (no 'host' VM OS) of another gaming front-end and the speed of it is great. I'm guessing the slowness has to do with running a system in a system in a VM (or something like that). That's cool. I just wanted to see it.
@dankcushions it’s about performance. On 2016 I can play eg. Die Hard Arcade with minimal slowdowns during QTE but overall game is pretty playable. With current mame it works in around 10 fps. Apart from that I have Mame2016 romset and don’t need to find another source for that.
I removed cfg file from arcade folder and I'm back on RGUI. Still having some problems as keys set in ES does correspond to those in RetroArch but I guess I have to do some further steps removing "broken" retroarch.cfg files from few places and then reinstall RA from setup script and hope it will fix it.
Thanks a lot for your help!!!!!!!