While Linux Mint may not be designed specifically for game compatibility, it is quite user friendly. The default desktop environment (cinnamon) feels a lot like windows.
It behaves in much the same way as other distros for steam games (check protondb for compatibility). I can't say how well it works for other games as I haven't tried.
The Linux Mint installer is fairly intuitive and easy to use. There is an option to install alongside your existing OS, and the included GRUB bootloader will let you select which OS you want to boot each time you turn on your computer.
I've tried many different distros, but I keep coming back to Mint for it's user friendly feel, and simple customisation options.