After testing out all of the supported EmulatorJS systems, here's a report of all the systems in the Retro Game Room that do and do not support EmulatorJS and its Netplay capabilities.

EmulatorJS Working
-3DO (still adding games)
-Arcade (only some games work so far)
-Atari 2600
-Atari 7800
-Atari Jaguar
-Atari Lynx
-Game Boy
-Game Boy Advance
-Game Boy Color
-MSX
-Neo Geo Pocket
-Neo Geo Pocket Color
-Nintendo 64 (some games don't)
-Nintendo NES
-PlayStation
-Sega 32X
-Sega CD
-Sega Game Gear
-Sega Genesis
-Sega Master System
-Super Nintendo
-Turbo Grafx
-Virtual Boy
-WonderSwan
-WonderSwan Color

EmulatorJS Not Working
-Game Boy Advance (fixed on 7/7/2022)
-Famicom Disk System
-Sega CD (fixed on 7/7/2022)
-Sega Saturn
-PCFX
-Turbo Grafx CD
-MSX (fixed on 7/7/2022)
-MSX 2


EmulatorJS Netplay Working
-Arcade
-Game Boy *
-Game Boy Color *
-Game Boy Advance *
-Nintendo 64
-Nintendo NES
-PlayStation
-Sega CD
-Sega Game Gear *
-Sega Genesis
-Sega Master System
-Super Nintendo
*Doesn't support system link, so you can only use this to spectate other players

EmulatorJS Netplay Not Working (but should)
-TurboGrafx (it's suppose to support netplay, but it doesn't work)


I'll try to get the things that should work, to work (at some point). I also plan to get a few features added for it, selecting your own games for netplay, submitting screenshots with it, saving and loading save states on the site, loading and sharing save states from other users, etc.

I just got the following to work:
-Game Boy Advance
-Sega CD
-MSX

I also added a few Atari systems.


EDIT: I got Sega CD games of all regions to work now. Previously, just US games were working, but I figured out that I can provide all of the bios files in a single zip file so that it can load whichever is needed based on the region.

I just added a bios pack for Arcade games, which improved the compatibility significantly.

I forgot to make an update regarding 3DO games. They're all finished being added