If you're referring to a toploader NES (NES-101), it does not support RGB out of the box, and actually only has an RF-out jack back there.

A top-loading Famicom (Famicom AV, HVC-101) instead has the Multi-Out port similar to the SNES, N64 and GameCube. However, it doesn't support RGB out of the box, and needs to be modified.

You can modify a NES-101 for RGB output as well, the issue is for the NES-101 you also need to also add the Multi-Out port to replace the RF output.

Typically the NESRGB board is what most folks will add to support RGB output. Again, for an NES-101 you have to physically add the Multi-Out port as well.

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With a Multi-Out port you now have new options for suitably modified consoles to go from the Multi-Out to Mini-HDMI with something like the RAD2X which has a vastly simplified RetroTink multiplier/upscaler inline to give you a "plug-and-play" HDMI output that detects Composite, S-Video or RGB and outputs appropriately without any need to configure. That cable works across the Famicom AV, SNES/SFC, N64 and GameCube. It adds about 53 microseconds of latency, or ~1/315th of a frame.

However you can still do Multi-Out to Composite, Multi-Out to S-Video, or Multi-Out to RGB if you wish to use some other multiplier/scaler such as an OSSC or anything else you have.

This video by RetroRGB will go over things: https://youtu.be/O4HBvpRIwa4

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Long story short, you can have an amazing picture, with a simple HDMI adapter, on nearly any old console at this point. You have to either learn to solder, or you can pay someone to do it. There's a lot of options from simply buying an upscaler and plugging whatever you have in, to modifying for maximum image quality and/or ease-of-use.

Generally, I recommend most folks "keep it simple" or at least have the "easiest to use" option (in lieu of maximum quality) on hand. If you can take it out of storage, hook it up, and start playing within 2 minutes, generally that removes the friction you'd have and you'll actually play it. Flash carts are also a great "friction remover".

For those who like their old Game Boy, Game Boy Color and Game Boy Advance, remember that the SNES had Super Game Boy/2, and the GameCube had the Game Boy Player (also supported GBA). There's a lot to be said for playing those handheld games on a TV, with a wireless Nintendo WaveBird controller.

Though for those chasing what's possible, those options exist too, but trade off that "pick-up-and-play" factor :)