@alphabetapie It depends on what you want to hide. There are a few cases that this might apply to.
For MAME/FinalBurn Neo bios files, store them in /home/pi/RetroPie/BIOS instead of in the arcade, fbneo, or mame-libretro folders.
For multi-disc games (except for Sega CD games), you can store the disc images in a directory outside of their standard ROM directory, and reference them with a .m3u file. For example, with a PS1 game, create a directory one level up from the psx folder called, for example, "psx.multi". Store the multi disc images in that folder. Place your m3u in the "psx" folder, and each line of the file should point to the disc's location. In this case, "../psx.multi/game disc1.cue".
For everything else, you can customize es-systems.cfg. Copy the original es-systems.cfg file into /opt/retropie/configs/all/emulationstation so that your changes will persist between updates, and edit the file. Each system will have a list of what file types they support, and by default will show them in both upper and lower case (for example .zip and .ZIP). Simply remove one of those (for example .ZIP), and then rename all files you don't want to show up in emulationstation with that extension. (game.zip becomes game.ZIP). The file will still be in that location, but emulationstation won't read it when building your game list.
Thanks for the info, much above is pretty similar to my current setup. Much appreciated.
I've got game collection art grouping the console games together and now i'm trying to hide the original emulators without deleting any of the games inside of them.
This won't work with custom collections. To quote @pjft, the developer of custom collections (original post here):
The custom collections rely on games that ES knows about.
ES only knows about games that it loads.
ES only loads games from systems that it knows.
ES only knows about systems defined in es_systems.cfg.
In short, removing a system from es_systems.cfg will remove games for that system from a custom collection.
This process involves creating a custom es_systems.cfg file so please follow the advice given by @quicksilver. Adding a new system in the default es_systems,cfg in /etc/emulationstation means that should you install an emulator at a later date, the file could be overwritten, removing the new system.
@battlecat One way to do this would be to do the following:
Scrape all of your roms to make sure all are listed in the gamelist.xml file.
Manually edit the gamelist.xml file (usually located in ~/.emulationstation/gamelists/<system>) to remove the unwanted roms.
From the main emulationstation screen, push start, then find the option in the menu that says "Parse gamelist.xml file only" or something like that.
Reboot your system, then enjoy!
This is how I hide the various bios files as well. Of note, if you add a new system or rom, you'll have to disable the "Parse gamelist.xml" option to see the new roms, unless you've scraped them already.