I'm pretty sure I don't need to be told how I can judge music on its own basis, regardless of context. At the end of the day, music is music. It might fit the game, as you suggest, but in which case I can't see it doing much to enhance the experience.
Take FFX's ending theme. I heard that on its own before I'd even played the game, and it was one of the most amazingly beautiful pieces I'd ever heard, even moving me to tears. Then I heard it in the context of the ending, and I was equally moved, because the ending to the game was not only wonderful but had a fantastic score to back it up.
And this is just one of many, many examples where I will hear a good piece of music on its own and be moved by it. Now, in the context of the game, it may serve to enhance it or, if the music is entirely inappropriate, can actually work against it. But that in no way should change the enjoyment of the music by itself.
That's not to say I haven't heard the odd track which I'd previously glazed over, but then later found I actually enjoyed more on having some context applied to it. That can be a situation where I think of music in a light I hadn't previously considered.
However, I have yet to witness an entire soundtrack of mediocre quality be lifted just by being in the context of something else. I have no doubt the music serves the game admirably, but I'm unlikely to appreciate it a great deal more other than those pieces in the score I already enjoyed particularly to begin with.
And I stand by my accusation that this is not the kind of fantastical score that I have grown accustomed to in the Final Fantasy series. And not even the kind of level I'd expect from Sakimoto - he's certainly proved he can do the unusual and whimsical with Gradius V, and there is none of that energy on show here.