You can make them game boy only but also compile to another target like windows or macos.

It will just look strange full screen on a 27 inch display for example.

You can also target phones were you upscale the img by 4 times or so and it becomes pretty playable.

Also you don't have to stick to hardware limitations but you can.

For some its fun.

But you can also learn a lot about hardware programming because these old consoles like the game boy are pretty simple and 8-bit. So its also great for learning.