Any simulation of scanlines I've seen is ultimately destracting and looks and feels 'simulated'. It doesn't make the experience feel anymore authentic.
Let him try it for himself; it's a matter of opinion.
Go to
mame's suplimenta artwork page, download the super small effects file, and extract them into your artwork folder. (
Examples on how the files look are linked from where you downloaded the zip.) Then change "effect none" in your mame.ini file to "effect
filename", where filename is the file you want to use of the ones you just downloaded.
I'm not saying it's perfect, it's not. But it's good enough for some people. (The higher res LCD and a matching effects file doesn't hurt, either.)
And note that using this can slow down mame if your video card isn't strong enough.