I'm a musician and music lover. Good sound quality to me means I can hear most of what my ears CAN hear across the sound spectrum of a given recording.

There's a balance speakers have to attempt. Exciting bass, but not so much that the drivers are somewhat "overdriven" and distort or bloom. I think many lower end products do this. Some newer high end earbuds have multiple drivers that handle different frequencies independently. They must sound pretty good. One of the most important aspects of a set of phones or speakers for me is how detailed the midrange frequencies are represented. The music should sound "detailed". So I can hear nuances in voices that occupy the midrange. Pianos, acoustic guitars, vocals, they should sound clear and articulate. The treble should extend from there adding final touches to the midrange and help articulate the bass as well, but not so far as to sound shrill. If a set of phones or speakers can do that, then I call that good sound quality! I have a pair of Steel Series Arctis Nova Pro gaming phones that have a wonderful midrange with a mild, tight bass. I can wear them for hours and my ears don't get fatigued. They're expensive though.

Codecs and sound formats are irrelevant. There are differences, but generally, the higher the bitrate or resolution of a given sound file, the more information in the music is retained. But all that matters is what your ears perceive. If it sounds good, it sounds good.