The Raspberry Pi Foundation's latest single-board computer is a compelling candidate for use as a retro games console. Not only is it the most powerful Raspberry Pi that the Foundation has released, but it can also tap into the diverse Raspberry Pi ecosystem.
Until now, the Raspberry Pi 4 has been incompatible with RetroPie, a popular and easy-to-use distribution for retro gamers. That has changed with RetroPie 4.6, although the developers have labelled it as beta support for the time being. Nonetheless, most emulators should now run well.
Now based on Raspbian Buster, RetroPie 4.6 includes RetroArch v1.8.5 and EmulationStation v2.9.1 among a host of other updates. The entire changelog is too long to post here, but it can be found at RetroPie should you wish to read it.
RetroPie 4.6 can be downloaded now for free. The distribution is not limited to the Raspberry Pi universe, either. RetroPie 4.6 runs on Debian, Ubuntu and several Odroid SBCs too, the installation instructions for which you can find under the Platforms section of the RetroPie Docs page.