Bah, I don't think you can have one 'best' musical artist - they're all so different and talented in so many ways.
I think a better question would be who has made huge contributions or influences...
Hank Williams (Sr.) drove so many of the country musicians you hear today. Garth Brooks took a nearly dying genre and catapulted it back to the top. While women like Dolly Parton (bless her heart, I love her to death) and Patsy Cline made huge inroads in country, Shania Twain really blew country wide open for female artists with a more modern style.
Duran Duran took a fledgling video music industry and power-jumped it into the monster it is today.
Elvis was a cross-breed rock-country genius who moved both genres forward from goody-two-shoes happy-happy sit-still-and-watch songs to something so energetic and emotional you couldn't sit still and everyone from your great-grandmom to your 15-yr old daughter thought he walked on water... not to mention the breakthroughs he made for all artists with nothing more than a shake of his hips (or would that be a hilarious pinkie-finger dancing?hehe) :P
Aerosmith is by far the only rock n roll band who has identified with EVERY generation for the past 40 freaking years and they're still going strong, still putting out new top-ten material and bringing the house down in live shows.
Metallica showed the world that heavy metal is more than just noise, those boys were brought up on classical music and opera and the influences are strong in their music; as evidenced so beautifully by the classical symphonies who play their songs (one of my favorites is Carol of the Bells w/ Metallica and the Tran-Siberia orchestra).
The Beatles of course get a standing ovation for bringing rock-n-roll to the American youth; sure R&R was around before that but even artists like Chuck Berry were "daddy's music".
2Pac *does* get props in my eyes, he took the soulful R&B sound and moved it into something that the youth could identify with - yeah Barry White and Marvin Gaye were serious figureheads in R&B but again, that was "daddy's music"; 2Pac along with LLCool J and Kool Moe Dee gave the youth their own sound. Too bad fuckheads like Eminem had to come along and ruin it.
And it just goes on and on and on....
I'm one of those musical mutts as well, although I prefer "eclectic to the extreme", LOL.
My favorite memories will be sitting in front of the record player all day and all night long as a kid with me, mom, and dad all fighting over which 45 would go in next... we'd hop from Charlie Rich to Elton John to Jefferson Airplane to Rush to Loretta Lynn to David Bowie to the Statler Bros to Rod Stewart to Neil Diamond to the soundtrack from Cats... starting at about 11am on a Saturday and finally ending around 3am Sunday morning.
And of course going to see Elvis live in concert and coming home with two black eyes because Mom had her hands on the binoculars and she was shaking so badly, lol.
