When it comes to music obviously there is a lot of subjectivity to it, sort of like with food. Yes, there are some things that would gag anyone with taste buds, but to a great extent it's a matter of what you have developed a taste for through continued exposure. There will always be people, especially older people, who find the music the kids are listening to now terrible, because their "taste" in music has been formed through exposure to something different.
I think much modern music is good for what it is, the question is whether what it is is good. A lot of the most popular modern (as in, the last five years or so) music is essentially dance music and is meant to get you excited. To the extent that it succeeds in doing so for the target audience it is good at what it is designed for, and it no doubt takes a kind of skill to accomplish that, and especially to accomplish it in such a way that anyone would also want to buy the song and listen to it outside the club and while sober.
Plato, I seem to recall, condemned certain forms of music whose purpose was emotional excitement rather than beauty, and also condemned novelty in music. I think it's a safe bet he would not have been a Gaga fan. We Christians take a more incarnational view of life and have a more balanced view of emotion and all the more arational aspects of human nature, though in general we agree with Plato that our lower faculties should be subject to our higher ones as much as possible, with reason as the highest faculty of our souls. But authentic reason itself reveals that a Vulcan-style impassivity (while suppressed emotions rage beneath the surface) is not the way for human beings to live.
For us Christians all things are lawful, but not everything is helpful. Listening to a certain kind of music isn't intrinsically evil, so far as I can tell. But will it help us grow as a person in the way God is calling us to grow? Or will it help us serve God and our neighbors? If not, maybe we shouldn't be listening to it at all.