Personally, I find most rap & hip-hop to be useless - there's simply too much cussing & violence. I love music, and when it's nothing but vulgarity there's simply no real value to it. I've listened to some Eminem and a couple of other rap 'artists,' and in my opinion it's crap. I do listen to rap, though - I listen to KJ-52, John Reuben & Toby Mac, who use nonviolent means to create rap music.
I don't listen to most modern music (Britney Spears, Christina Agulara, any boy bands), mainly because I simply don't see much use in it. Most of it is about sex (see the Britney Spears lyrics above), and for the young women singers, it seems to me that it's all about marketing their sex appeal - even moreso than their music. Both of these styles promote promiscuity and violence, and I simply cannot in good conscience support that (and I know that many people disagree with me).
Anyway, that's my opinion of modern music.
I mainly listen to Christian music - The Newsboys, Switchfoot, Jars of Clay, Jennifer Knapp, Third Day, Ginny Owens, etc.
I love classic rock - Pink Floyd, Skynard, Bob Seger, Buffalo Springfield, Bruce Springstein, The Who, Joe Walsh etc. (I inherited my love for classic rock from my father).
I also love Paul Simon, Bob Dylan, Peter Paul & Mary, and those kinds of artists.
My all-time favorite artist of all time, though, is Bing Crosby (I also like Frank Sinatra, Dean Martin & Glen Miller).