Create a folder in your home folder - I call mine "Dock."
Create a subfolder inside of it called "Arcade."
Open Applications and drag all Arcade games into the ~/Dock/Arcade folder. The Finder should create aliases.
Drag the Dock folder into the Dock next to Downloads.
Right-click on it to set appearance etc.
You can do this with any app or document.
I have Games, Music apps, Productivity, Utilities, and VMs there.