If you’re not one to emulate, and you want to get the most out of your N64, you might want to look into acquiring a cheap S-Video AV cable for your console from eBay.
S-Video is the best method of maximising the video quality from your N64 without having to full-on mod it: it splits up the colour (chroma) and brightness (luma) information into two separate channels, which are usually combined when being delivered to your TV through a (yellow) composite cable. The result is that S-Video retains and preserves video data better than both RF-modulated and composite encoded video.
S-Video is a particularly practical way of improving picture quality in older consoles because many issues with such consoles’ video can be attributed to the way chroma and luma are encoded. Interference between colour and brightness information is frequently the culprit for bad picture quality, and not an outright lack or loss of picture definition (many older consoles being designed for the purpose of interfacing directly with an analogue TV, its circuitry being timed to its scan lines). A classic example of chroma-luma interference in games due to imperfect (and unavoidable) composite video encoding is dot crawl.
The trouble with many of these N64 S-Video cables is that they produce an image on your TV that is too bright. There is a fix for this, and it is pretty simple. The diagram above illustrates resistors placed between ground and every video channel of an AV cable, but all that is sufficient is that a single resistor be placed between luma and ground. Using a 1K-ohm trimmer pot is a fairly convenient resistor to use because it allows one to adjust the picture brightness very carefully. Although it takes some fairly patient soldering, the results are definitely worthwhile. Being able to play Banjo Tooie, Perfect Dark or Rogue Squadron in S-Video in 640 x 480 is a fairly rewarding experience. What I found pretty damn gratifying was being able to properly resolve a couple of my favourite Jet Force Gemini levels!
On the left you’ll find some before-and-after images from an S-Video hardware mod undertaken on davidhowland.com. While the difference in video quality is partly exaggerated by camera focus, you can see how the brightness and colour information have interfered with one-another.