Trying to simulate NTSC TVs is a bit like trying to simulate old audio recordings being played through the old horn phonographs when we have the master recordings available and modern high fidelity audio equipment to play them back on. In this case, we have the bit-identical ROMs available and much more accurate RGB computer monitors.
The games I played were
those images on an NTSC television, with the dancing dots and muddy colors; this wasn't just a poor reproduction of the real game that existed elsewhere (crappy arcade conversions aside).
Some game developers may have drawn graphics for an RGB monitor, but the good ones drew them for a TV and took advantage of its characteristics. Blurring allowed dithering without looking like a checkerboard (as it looks with crisp RGB). Color bleed allowed more apparent colors than the system actually generated. Even the pixel artifacts meant that a simple vertical edge wasn't plain. A game like Metroid or Blaster Master wouldn't have been near as textured on an RGB monitor.
So nowadays we have the ability to make these games look much better than they did when we were originally playing them.
The purpose of a console
emulator is to accurately reproduce what that console looked and sounded like, and not to intentionally alter how it works. I don't have a problem with enhancements, they just play a secondary role and should be clearly distinguished for someone who wants as precise a simulation as possible. They are also entirely subjective. For an example of enhancements gone haywire, take a listen to what has been done to audio CD quality over the past decade, in the name of "making it louder without you having to turn up the volume". I think the drive to try to enhance everything is a dead-end. I stopped turning my stereo's treble and bass knobs up to the max all the time and my ears have thanked me ever since.