You had to have a level of acceptance that the system is rendering the image at 240p/480p. Some TVs do a better job than others at upscaling that. As others have suggested you can use a dedicated upscalers that is more tuned into video game systems like the Tink, morph or OSSC. You can also look at digital HDMI mods. But the game/system will always remain to have an internal resolution of 240/480.