Your best option is Retroarch, it can emulate way more than just gameboy. But if you are looking for something lightweight and easier to use, try lemuroid https://f-droid.org/en/packages/com.swordfish.lemuroid/
Have you try retroachievements.org ? It really makes playing old games a new experience by adding a more challenging and competitive aspect.
On Android you can use seal. By default download the thumbnail of the video as cover, the channel name as artist and the video name as the song name. You can also download entire playlists.
Your best option is Retroarch, it can emulate way more than just gameboy. But if you are looking for something lightweight and easier to use, try lemuroid https://f-droid.org/en/packages/com.swordfish.lemuroid/