So a bit of an update. Since I was no longer using my RPi3 (I had ordered a XU4) I decided to experiment with it (the RPi3) more than I had before and I installed Lakka on it, and it worked perfectly. Out of the box the games look amazing and the (few) that I have tried, both SNES and PS1 have run perfectly.

This tells me that there isn't a problem with the pi, the power supply or the sd card, its just something different in the versions/configuration in RetroPie. For clarity sake, I always installed RetroPie from official builds, and tried multiple times, always trying to use it with out of the box defaults first.

I gave the RPi3 away, so I can no longer test with it (the XU4 runs circles around it) but it is good to know that it was at least capable of running the emulators that I thought it wasn't.

I have not put RetroPie on the XU4 yet, I am trying to get a decent set of benchmarks (games that run smoothly in Lakka) to compare.

I'm pretty sure Minecraft for Pi only utilizes keyboard and mouse. This is an old version and I don't believe it's been worked on in years, it's just there for fun.

If you need help we would need the system information from this link in order to know what you are working with.

https://retropie.org.uk/forum/topic/3/read-this-first

[SOLVED]

I noticed that in the main retroarch.cfg file there was a setting as follows:

# Toggles fullscreen. # input_toggle_fullscreen = f

I wasn't aware that a commented line means that the "default" is still enabled. (ie: "f" is still enabled to toggle fullscreen).

I've now changed this to the following (ie: replaced "f" with "nul") and the "problem" is now resolved:

# Toggles fullscreen. input_toggle_fullscreen = nul

but including retro pie I think you might just make with exactly 16 GB

@mitu Perfect! Now RGUI it's back.
menu_driver = "xmb" was in snes/retroarch.cfg, deleting that line fixed it.
Thank you very much :)

@ashthekid what is your hotkey? Do you press select and start to exit? It should be your hotkey + x.

Its quite ok, if you ask me. I use a three meters long HDMI cable and it does not bug me while playing :)
At first I wanted all ports at the top, but it didn't fit :(

wow that was quick. It was the rom indeed. Thanks Mitu for your quick support. It finally works...

Ok, Scrolling to the Left works, but i only get to Spanish before it Crashes. No German :/

@lostless

Try it again later (if you have not done so already). Had the same issue and just worked on another system and went back to it the next day

Report the issue here:
https://github.com/libretro/snes9x2010

Looks good

Well I've tested Sega CD and 32X on my Pi Zero. I used the overclock I mentioned above but with overvolt 2 instead of 6. Sega CD works flawlessly on FMV games and games that use scaling/rotation. Sega 32X is so close to full speed it hurts, but its not quite there. I'm sure if I could squeeze another 100 MHz out of the CPU safely it would work at full speed. It's funny because I remember 32X working good on my Pi1, just not PSX or above. That was a few RetroPie versions back however. This will eventually be a handheld system so active cooling is not really an option. As a result I will likely have to leave 32X out unfortunately, unless performance improves when I lower the screen resolution for the LCD. Out of curiosity, has anyone ever pushed a Pi1 or Pi Zero to 1100 MHz? If so was it stable? How about temperature under load?

Just for confirmation, I tried Starfox 2 Zipped on 'lr-snes9x2010' and it ran fine (tiny bit of sound stutter here and there). Maybe you had some dodgy compression on your Zip file.

@mitu Alright, it's the lr-snes9x2010. Thanks for your help with that one.

Did you follow these steps: https://github.com/RetroPie/RetroPie-Setup/wiki/Running-ROMs-from-a-USB-drive#automatic-mount-easiest-method
As that is in my opinion the easiest way.

@gtr63 Maybe you set SNES up first to test before setting up the whole USB mounting thing. It's easy to forget what exactly you did when first setting up, especially if you are not experienced with RetroPie or Linux.

Thanks @petrockblog!
I just tried it out using some stipped wire.
Connecting Plyr 1 GND or Plyr 2 GND with Player 1 B for a short moment will indeed "reset" out of the current running game!