the genre and marketing is very closely related, IMO it's a combination of bad music and bad meduims/formats. You wonder how in the world some of these fools get on MTV and all the fame with such bad music while somewhere out there some indie band is probably making some of the best music (n)ever heard. My only theory is that the music industry is all about politics, and knowing the right people, and that the big east/west coast gangs have strong influences in the record labels, thus this rap/hiphop pop trend is being pushed so hard. Modern rock is also pretty bad, but has a much smaller footprint in the music scene. Watch an hour of mtv and you will hear 15 rap/hip hop songs, 1 or 2 modern rock, 3 or 4 pop or 'idol' songs, and 0 songs worth listening to.
btw, I'm not ragging on rap and hiphop as a genre, it's the stuff that is playing over the airways and on tv that I can't stand. I am sure there is some amazing hiphop and rap music out there, this applies to every genre! However I notice whenever a friend brings a pop rap/hh cd over to play on my hi-fi system, the artist's recording approach is not to my taste at all. Someone mentioned earlier these cd's are designed to sound good on ipods and boomboxes and I totally agree. No imaging, no attention to detail, little regard to recording enviroment, just a conglomerate of computer generated drumbeats with the bass jacked way up, and a not so musically entertaining voice on top.
Lastly, you must notice that only pop/rap/hiphop/idol etc artists do the advertising in their videos. You never see a modern rock group shamelessly giving plugs to caddilac escalades, bmws, ipods, cellphones, clothing, etc IN their music videos. Rock videos are ususally shots of the band playing, while rap and hiphop is mostly sexist, materialistic, sometimes animalistic displays of vulgarity. What other genre of music video can you break the law, escape from the police in your shiny pimped ride, and stop to pick up 3 or 4 scantily clad women while tugging at the enormous diamond studded chain on your neck?