In case the title isn't obvious enough:

Pop: Kylie Minogue
R&B: Usher/Next
Rap/Hip-Hop: Bone Thugs n' Harmony, Outkast
Alternative: Toby Lightman(modern alternative)/Bonnie McKee(modern alternative)/Green Day(punk)
Rock: Alanis Morissette/Five For Fighting
Country: Shania Twain
Electronica/Dance/Trance: Frou Frou

I didn't want to go overboard with too many sub-genres, so eh.