Britney Spears' music. Okay, I can criticize it for being commercial, unoriginal, and derivative and wish a certain torturous death upon anyone who buys her cd.
One thing I can say in Britney's defense in the "good vs valuable" debate, is that her video performances still remain marginally pleasurable and therefore have some value with the sound turned off, which is more than you can say for some old crusty hippy fella playing his art.....
(Well I found it funny anyway....
)
While I'm not really attracted to Ms. Spears, I do agree wholeheartedly with what you're saying. I've got a recording of that Kylie Minogue video that I can't stop watching. I'm thankful I don't feel that sensation for the crusty hippy fella. That's not to say that someone doesn't.

I do have to say that I did have an interesting sensation at a live performance by classical guitarist, Sharon Isbin. I still don't remember exactly what music she played, though. It could have been "Who Let the Dogs Out." It just didn't matter.
Regarding value, I do think it's important not to compare apples to oranges. How can a pop song or performance be judged by a completely different set of criteria than for which the song was intended to fulfill? Likewise, I don't think a sonata by a historic classical composer should be judged by hip-hop criteria. They're two different animals. To say one is overall better than the other is to say that one color is overall better than the others. I don't think a pale shade of green is a good color for a school crossing guard's vest, but I do think it's a pleasant color for the school's interior. Likewise, a dayglo orange room isn't exactly conducive to quiet concentration, but it's great to get our attention where it counts.
The pop top 40 is primarily determined by 15 year old girls, not 45 year old eggheads.
My 75 year old dad is a George Jones/Conway Twitty kinda guy and no amount of explaining or exposure to Metheny or Godspeed You Black Emperor is gonna have a lot of effect on his preferences. Perhaps, expanding his horizons can be viewed as an admirable thing on one level, but as Kai has been hinting at, the attitude assumed by the "superior" individual is more than a bit unsupportable, philosophically speaking, unless your philosophy is tyrannical ethnocentrism.
My dad's set of formative experiences is different from mine. The same is true of 15 year old girls. While I hate taking the stance of a sackless relativist, I can't think of any supportable reason why their music is inferior to mine, provided each is judged by its own criteria.