Here are some samples of what I like. Some of the artist/genre classifications could probably be more correct.
Acoustic: Paco De Lucia, Al Di Meola, Michael Hedges, Phil Keaggy, John McLaughlin
Alternative: Audioslave, Cold, Foo Fighters, Nirvana, Smashing Pumpkins, Tool, Splender, Staind, Three Doors Down, Vertical Horizon, Weezer
Bluegrass: Iron Horse
Blues: B.B. King, SRV
Christian rock/metal: Bride, Deliverance, Guardian, Idle Cure, Petra, Shout, Stryper, Whitecross, Whiteheart
Classic rock: Aerosmith, Boston, Cream, Deep Purple, Emerson, Lake & Palmer, Foreigner, Jimi Hendrix, Journey, Led Zeppelin, Queen, Santana, Thin Lizzy
Classical: Bach, Beethoven, Chopin, Mozart, Rachmanninov
Country: Susan Ashton, Kathy Matthea, Shania Twain
Electronica: Anything Box, Aura, Chicane, Depeche Mode, Echoing Green, John Lawry, Paul Oakenfold, Michael Pinella, Jordan Rudess, Derek Sherinian, T.A.T.U.
Film scores: Braveheart, Gladiator, Jurassic Park, Last of the Mohicans, Schindler's List, Star Wars, Titanic, many more
Funk: James Brown, Cameo, Commodores, Earth, Wind & Fire, Parliament, Victor Wooten
Instrumental: Marty Friedman, Eric Johnson, Tony MacAlpine, Yngwie J. Malmsteen, Joe Satriani, Steve Vai
Latin: Enrique Iglesias, Arturo Sandoval
New age: Secret Garden, Yanni
Nu-metal: Killswitch Engage, Passenger, Spineshank, Stuck Mojo, System of a Down
Other: Bananarama, Little River Band, Sade, Type 0 Negative, ZZ Top
Pop: Coldplay, Dido, Celine Dion, Amy Grant, Whitney Houston, Elton John
Progressive rock: Explorer's Club, King's X, Liquid Tension Experiment, Pain of Salvation, Planet X, Porcupine Tree, Rush, Yes
Rap: Outkast
Reggae: Bob Marley
Rock: Black Label Society, Pink Floyd, Slash's Snakepit
Ska: Insyderz, Mighty Mighty Bosstones, Supertones
And for my top 2, most listened to genres, metal and jazz.
80's: Impelitterri, Racer X, Ratt
Classic metal: Black Sabbath, Iron Maiden, Judas Priest, Ozzy Osbourne, Scorpions, Van Halen
Melodic death metal: Arch Enemy, At The Gates, Dark Tranquillity, In Flames, Shadows Fall, Soilwork
Other: Amorphis, Children of Bodom, Control Denied, Demons & Wizards, Drain sth, Extreme, Fear Factory, Galactic Cowboys, Katatonia, Lacuna Coil, Nightwish, Pantera, Rammstein, Sentenced, Warmen
Power metal: Edguy, Evergrey, Gamma Ray, Helloween, Royal Hunt, Sonata Arctica, Stratovarius
Progressive metal: Andromeda, Dream Theater, Into Eternity, Nevermore, Opeth, Queensryche, Savatage, Spiral Architect, Symphony X, Tourniquet
Thrash/speed: Anthrax, Iced Earth, Megadeth, Metallica, Testament
Bebop: Dizzy Gillespie, Thelonious Monk, Charlie Parker, Bud Powell
Cool/modal: Dave Brubeck, Miles Davis, Bill Evans, Stan Getz, Vince Guaraldi, Lennie Tristano
Fusion: CAB, Chick Corea Elektric Band, Gambale/Hamm/Smith, Mahavishnu Orchestra, Niacin, Return To Forever, Weather Report
Hard bop: John Coltrane, Dexter Gordon, Charles Mingus, Sonny Rollins
Smooth jazz: Dancing Fantasy, Richard Elliot, Paul Hardcastle/Jazzmasters, Lee Ritenour, Grover Washington Jr.
Sorry for the novel.