The emulator should be able to scale it to your native TV screen's resolution.
EDIT: What I've other people recommend - and it sort of makes sense - is to try and run the NTSC version of a ROM when possible. NTSC ran at almost 60hz, similar to the modern displays.
Bingo - that's exactly what I just did before I'm reading this :-)
Set boot config to CEA-4, removed default emulator video choice from on-game startup menu and sorted out my ROMs so now it's all USA (NTSC) versions.
Now it's all perfect.
As always: Thanks buddy for your good explanation and clarification.