How to make N64 look good on HDTV?

Unfortunately there's not a lot you can do.

HDTVs will always upscale any incoming signal to their native resolution. This means if you have a 1080p HDTV, everything gets upscaled to 1080p. Old video game consoles used standard definition (SD) which was only 480i. This means they only send 240 lines of data to the TV at any given time. The TV then has to stretch those 240 lines to fill 1080 lines.

The bars on the sides are because SD TV signal only had an aspect ratio of 4:3, whereas HDTV is 16:9. There is no way to tell your HDTV to shrink the image any further.

The only thing you can do, really, is use a smaller screen, or an old SD TV set.

That video is 70 years old. (Standard def was created in 1948 and the old standard def game systems have to honor this old, old video standard).

Standard def was designed to fill a nine-inch screen. That is nine -inches only.

You are also probably using a yellow "Composite" cable which is the worst possible type of video connection.

Take this old, nine-inch video and magnify it and display it on a modern High Resolution display and you see all the noise, grain, washed out colors, etc. that is from the 70 year old video standard.

There is nothing you can really 'adjust' on your HDTV to make this crappy image look better.

S-video will give you the first-class feasible photograph, however that's now not announcing a entire lot as it is going to still only be 480i - same as your non-HD tv channels. Your television will then upscale the photo to its native decision (720p, 1080i or 1080p) which will make the pics look "blocky" or "jagged". Basically the identical crisis you see on computers when you attempt to zoom in a small photo photo.

Like others said nothing you can do but find an old TV to play it on. Even the PS1 games that are sold on the PlayStation's PS3 network look terrible when playing them.