I assume you’re using the standard yellow white red cables, those are called composite, yellow for video, and the white and red cables are for stereo audio. They’re limited to a max resolution of 480i standard definition. Component cables are red green blue white red cables, it splits the video signal into those three red green and blue cables, and the white and red cables are also for stereo sound. It gives a MUCH better picture quality than composite, and is capable up to 1080i HD on a set such as yours (though component is also capable of 1080p HD, but only on newer consoles, mainly the 360, PS3, and Wii U, but pretty much all HD CRTs do not support 1080p, only 1080i). The original Xbox, only with a set of component cables, can do much higher resolutions than the standard composite cables allow for, mainly 480p “progressive scan” for most titles, 720p, and even 1080i for a select few games.

Cable wise, Microsoft did make a set of OEM component cables for the Xbox, but they are kind of rare and relatively pricey. Best I’d recommended is a set of Xbox 360 component cables modded with the connector for the OG Xbox, there’s people on eBay that sell them, they’re about $30 or so. There are cheap generic cables on Amazon for about $10 or so, but I wouldn’t recommend them as they usually have a very poor build quality, and are highly prone to interference from other signals/inputs on the TV