The idea of good music and bad music is subjective sadly. Anyhow, basically, there's no true definition for "Good" and "Bad" music...
However, I have a definition of "True Music" in a way... To me, true music is the expression of emotion and feeling through sound and such. That's why I could never really consider someone like Soulja Boy as a "musician", all he does is rap about absolutely nothing actually... He just says crap to make money from what I can tell, it's odd but when a musician hears music, the ones that are expressed truly often feel like the best. Even in the gaming industry, the "importance" of music has diminished a bit in my opinion. I don't mean the actual importance of music, rather, the values of it's importance.
Honestly, I don't think people realize how important music can be, especially in video games. One of the reasons I felt a hint of fear in Silent Hill 1 was because of the ambience the music caused. The reason I felt so pumped up in Street Fighter 2 was because of the music as well, and both the musicians for the games were very passionate about what they were doing. Hell, the guy who did Silent Hill 1's soundtrack took it quite seriously and felt as if he was "the man for the job". (Akira Yamaoka)
The creator for Street Fighter 2's soundtrack was Yoko Shimomura, a person who deeply cares about music is inspired by her passions and emotions. It feels like the industry of both music and gaming industry don't care as much about these things (With the exception of a couple companies). Anyhow, what are your opinions on this?
If I'm ever to make it to the industry (And I can only damned as much hope considering how greedy some video game industries are seeming), I'd try to find a way in order for the music to be good in the games, even if that includes doing the soundtrack myself for free.