A good enough Game Launcher, Playnite works with emulators, Steam, GOG, Itch.io and Humble Bundle (along with others I won't touch). It catalogues all your games, and makes customizations (launch options, art, etc.) simple. It has a skinnable UI, and the skins are written in CSS, so that's great, too. Sadly, it's Windows only.
GOG Galaxy 2.0 came out recently and it's kinda awesome. You can add your Steam, Epic, and other libraries to it easily. It doesn't handle emulators (AFAIK), but if you use Retroarch, you probably don't need a launcher for your emulator anyway. Sadly, it's not available on Linux (yet), and the customization options are very limited - there's no theming (yet), for instance. Anyway, a great launcher from a great store.
You can technically add all sorts of games - including emulated ones - to your Steam library. Unfortunately, it is and always has been a pain in the ass, and there's little sign of that changing. The custom skins can be cool, and it works on basically every platform (although getting it going on *BSD is difficult to say the least).
Probably the best overall cross-platform launcher/library manager. It's open source, very customizable, and doesn't hide any features behind a paywall. That said, it's not the easiest one to work with, and it can be a bit fiddly to work with overall. Still, with the right configuration, it can look amazing and run like a dream.
Your best option on Linux (and probably FreeBSD with a compatability layer), Lutris is a powerful game library manager and launcher. It lets you set up very individualized launch setups, is skinable, and cheerfully manages your emulation. I dearly wish it was available on Windows and OSX, because then it would be the best cross-platform option.
So, I love the GNOME desktop. Gnome 3 works the ay my brina works, I guess, and I love the look and workflow paradgm. Most of their additional apps are great, too. But GNOME Games is a bit lackluster. It looks good and integrates well into the GNOME Shell, but it requires hunting down config files for any advanced configuration - and there isn't much in the way of options even then. It works well within its narrow edge, but isn't good enough if you have games outside of your Games folder or need any advanced options.
