Just got Garou running in Retroarch.
It's damn glorious.
Simplified instructions for anyone wanting to do that:
1. get retroarch
2. get the Arcade (FB Alpha) core (from menu, online updater, then core updater, choose Arcade (FB Alpha)
3. exit retroarch.
4. Run the .exe you got for the game from humble, which installs it.
5. go to the install folder for the game. select "gamename.zip" (e.g., garou.zip) and neogeo.zip and copy those files to a folder to hold your retroarch roms.
6. boot up retroarch. Load Core (Arcade (FB Alpha)). Load Content (your game rom, not the neogeo.zip rom).
7. enjoy! add scanlines with shaders (I'm using crt.hylian.simple right now)
SSV and Last Blade next!