Anyway, to get back on track:
As someone already pointed out, you have to consider the purpose of music in a medium. Music is not always intended to be a standalone product--very often it is designed to complement film/video games (think "incidental music", ambient soundscapes, music to foster a certain mood/atmosphere, etc.).
So...by design, some music in video games (RPG's) are "lackluster"... but, wait, it gets even better: sometimes a good song, repeated for the millionth time, becomes unbrearably grating. The cute, catchy song is a dagger to the groin. That sweeping, triumphant orchestral piece becomes a hackneyed mound of damp shite.
And thus we enter the House of Muzak, where, by design, music is preemptively banal. YES, that's right motherf*cker, it is banal by design.
Now, you might scoff at the notion, but it actually isn't such a bad idea when players spend hours upon hours listening to a particular track of music.
I personally feel that ambient soundscapes should be used in these situations--they are less grating then Muzak and can be much more effective nurturing appropriate moods.
I have never really researched/argued this before, but I will suggest that part of Metroid's (NES) brilliance is the hybrid ambient+simple melody formula that was used in parts of its soundtrack. I'm not saying it was perfect (the "loops" are far too short), but it was an effective way to be catchy, build atmospheric soundscapes and transcend the typical (generic) "standalone song" mentaility to video game soundtracks.
Shite, I've been ranting for too long.
Bottom line: mediocre by choice, or by incompetence?