I think Sturgeon's Law definitely applies in this situation: 90% of everything is crap.
I studied classical piano and pop organ for many years. I played clarinet in marching bands for years as well, and played keyboards for a group that was doing 1940s big band songs. I also taught myself bass, mostly by playing along with Rush, Iron Maiden, Megadeth, Led Zeppelin, Black Sabbath and Tool. And I picked up some guitar too. I had a friend in high school who was trying to write house, Euro and freestyle dance music, and sometimes I'd help him work out synth and bass parts.
I was in high school during the grunge era, which was also the techno/Eurodance era, the goth-industrial era, and the groove metal era. And many of my friends have a theatre background and turned me on to musicals and showtunes. Plus I've always loved soundtracks, both from movies and video games.
I'm also in a job where I buy music CDs for a mid-sized Canadian library system that serves a half-rural/half-urban community, and I need to have at least a superficial understanding of most genres.
So in short, I have listened to and liked a lot of different types of music. I basically divide music into two basic categories: stuff I like, and stuff I don't like. I generally don't like rap, country music, R&B, or indie rock. But I have found songs and artists in those genres I like very much. Conversely, I love metal, industrial, and goth music. But there are plenty of artists in those genres I can't stand. And sometimes I love the music but can't stand most of the fanbase. (metalheads) I also appreciate the craftsmanship behind some pop hits, even if I don't like the actual song.
However, I find it harder to like most mainstream pop and rock these days. Part of it is the Loudness war [http://en.wikipedia.org/wiki/Loudness_war]: I'm a bassist and keyboardist, and if I can't pick those parts out of a mix, I get really irritated. But a lot of it is that other genres have broken off and formed their own subcultures that don't really need mainstream affirmation to exist anymore, and the internet's made it easier for once marginal artists to find fans and distribute their music. (The dark cabaret/steampunk music I currently obsess over is never going to make Top 40, but I'm still happy it's out there.) So even more than in the past, the mainstream represents the lowest common denominator.
That said, I like Lady GaGa too. While I find half her songs dull or stupid, some of her hits are undeniably catchy and cool. And I can't turn away from the spectacle of GaGa: it's like watching a schoolbus on fire going over a cliff--I have to look!
Have fun at her show!
Have you heard their new album yet?
