I don't think Bob Marley, Metallica and 2Pac should be on the list. I'm taking influence on the same level as Skummy is, as in they should have changed/introduced/added to the genre of music they partake in. I suppose Metallica slowed thrash down a bit, but then other thrash bands haven't followed their example. I don't know too much about reggae, but Marley strikes me as the commercial epoch for reggae and while people like Lee 'Scratch' Perry were taking it in other directions Bob was peddling similar sounding stuff out. 2Pac introduced the idea that you can't become a criminal once you become a successful rapper, rather than the other way round, but his influence on music is less. Hip-Hop is a genre that is perhaps more reliant on the producer than the actual rapper who is getting the fame. If you wanted to throw in an influential 90s hip-hop person, Dr. Dre or Wu-Tang Clan (more specifically RZA) would have been better choices.
Link Wray and James Brown are both worthy contenders. I'm now off to see who I voted for (probably Metallica, Bob Marley, 2Pac and Frank Zappa).