I think impact depends on the genre (or culture) someone helped popularize, so looking at it that way, i would say.
Rock N Roll - Elvis Presley, Chuck Berry, Little Richard, Bo Diddley.
Hard rock - Rolling Stones, Cream, The Who, Led Zeppelin.
Pop - Michael Jackson, Prince, Madonna.
Funk - James Brown, Funkadelix, Sly & Family Stone.
Soul/R&B - Ray Charles, Stevie Wonder, Marvin G
aye, Aretha Franklin.
Thrash/Speed Metal - Metallica, Pantera, Slayer.
Metal - Black Sabbath, Iron Maiden, Judas Priest.
Pop Metal - Van Halen, Def Leppard, Motley Crue.
Punk - The Ramones, The Clash, The Sex Pistols.
Hardcore - Misfits, Black Flag, Dead Kennedys.
Pop Punk - Green Day, Blink 182.
Prog - Pink Floyd, Yes, King Crimson.
Alternative Rock - Velvet Underground, The Smiths, REM, U2.
Indie Rock - Sonic Youth, Pixies, Pavement, My Bloody Valentine.
Grunge - Nirvana, Pearl Jam, Soundgarden.
New Wave - Blondie, Talking Heads, Devo.
Electronic - Kraftwerk, Brian Eno, Depeche Mode.
Disco - Bee Gees, ABBA, Donna Summer.
Psychedelic - Jefferson Airplane, The Doors, Love, Jimi Hendrix.
Jam Bands - Grateful Dead, Phish.
Country Rock - The Eagles, Gram Parsons.
Southern Rock - Lynyrd Skynyrd, Allman Brothers Band, CCR.
Goth Rock - The Cure, Joy Division, Shoixie and The Banshees.
Reggae - Bob Marley, Jimmy Cliff, Peter Tosh.
Pop Rock - Fleetwood Mac, Rod Stewart, Steely Dan, Rod Stewart.
AOR - Boston, Meat Loaf, Journey.
Folk Rock - Bob Dylan, The Byrds.
Rap/Hip Hop - Public Enemy, Run DMC, Beastie Boys, NWA.
Glam Rock - David Bowie, T Rex, Mott The Hoople, Iggy Pop.
Britpop - Radiohead, Oasis, Manic Street Preachers.
Trip Hop - Portishead, Massive Attack.
Rock Music In General - The Beatles.
Well you get the point, i could cover every genre in existence, but i think i've done enough.
