First off, before I answer the question, let me offer some opinions on your selections.
Vocalists
1 Eddie Vedder - eh... nobody ever claimed the guy could sing, and while I'm no fan of Pearl Jam, they wouldn't sound right with a guy that carried a 5 octave range
2 Jon Bon Jovi - depends on what era... prior to the New Jersey album, JBJ had an excellent and very capable voice. However, he blew his voice out on tour in support of Slippery When Wet, and he's been doing that annoying sing-through-the-nose crap ever since.
3 Brian Wilson - I've never had an issue with Wilson's voice, and it amuses me that some one would single him out when there are guys like Chad Kroeger or Scott Stapp running around.
4 Jimi Hendrix - Like Vedder, nobody ever claimed the guy could sing, but it's all part of the package.
5 Anybody That Screams And/Or Grunts Instead Of Sings
Guitarists
1 Richie Sambora - Sambora is a very talented and qualified player, but I think his abilties are dumbed down within the constraints of the Bon Jovi catalog. You're obviously not a fan of the band, so I'd say it's safe to assume that you haven't heard the song "Dry County".... one of the best blues based rock solos I've heard in many years.
2 Mick Mars - Agreed, but... Mars' abilities have been limited due to his Krohn's (?) Syndrome for years. I happen to have the aquaintance of some one who played with Mr. Bob Deal before he became Mick Mars, and by all accounts, he was a solid guitar player.
3 C.C. Deville - Yeah, I must admit, CC is a hack.
4 Vivian Campbell - Over rated? Absolutely. Top 5 worst ever? No way. Campbell was an absolute guitar god during his Dio days. Like Sambora, his playing has been dumbed down over the years due to the restraints of first Whitesnake and then Def Leppard.
5 Anybody From Nickelback MCR or such. - Can't argue with that.
Now... worst vocalist / gutarist.... in my most humble of opinions....
Voclas:
1. Chad Kroeger - You want to end the war in Iraq? Simple. Just blast Nickelback at top volume over the country, and the extremist / terrorist in Iraq will be killing each other to get out.
2. Kurt Cobain - The man destroyed rock music in the United States single handed. No style, no talent. He's reveered today because he killed himself. Some hero. Yeah, I want my son to grow up to be just like him... a strung out heroin addict who couldn't hack it at the game of life. Then again, if I slept with Courtney Love, I'd blow my brains out too.
3. Johnny Rotten - Sorry, but there's nothing even remotely redeeming about his voice... that's not to say it didn't fit the music.. but man did he suck.
4. Stephen Pearcy - The most over rated vocalist of the most over rated band to come out of LA in the 80s.
Guitarist
1. Kurt Cobain - See above
2. Anybody else that has attempted a guitar solo since about 1991. People jump up and down about the image concious 80s, but at least those guys could actually play.