(Nice. I listened to Maggot Brain twice yesterday.)
Shania Twain definitely. She had a life-sized cardboard cutout display is the mall when I was young that made me feel kinda funny.
How about David Bowie vs Frank Zappa?
Bowie. Zappa had some interesting music, but was incapable of expressing any emotions but scorn and disgust. That gets old in a hurry.
Buffalo Springfield or Jefferson Airplane?
*Mothership Connection *makes it an easy win for Parliament.
My dad played Surrealistic Pillow non-stop when I was growing up and I’ve only heard “For What It’s Worth” from Buffalo Springfield proper (and I’ve learned that researching these answers only results in me getting ninja’d), so I’ll go for JA.
Two rappers that emphasize their middle names: Aubrey Drake Graham or Kendrick Lamar Duckworth?
O Thudlow, you really “should” listen to Marvin. His arc is profound, from Motown Pop to duets with Tammi, to What’s Going On and Got to Give it Up. He’s who broke Stevie open - What’s Goin’ On freed Stevie’s hand.
Have you heard him sing the National Anthem? 
Hehehe, I was actually referring to the Wonder vs. Gaye setup. I hemmed and hawed about that one until things had passed me by, and I was lucky Sabbath vs. Purple had already been plucked.
But yes, Wonder’s records show off more musical virtuosity, but he and Gaye have a similar vibe. If you like one, you’re very likely to enjoy the other.
I’ll Take Kendrick Lamar.
How about Stravinsky vs. Tchaikovsky?
Stravinsky, but it depends what day it is.
Barbra Streisand vs. Celine Dion
(I’d really like to see this as a bare-knuckle boxing match)
Streisand.
Yanni or Kenny G?
Yanni. Because, though I dislike them both, Yanni is fun to say. Yanni, Yanni, Yanni.
Nick Drake or Richard Thompson?
I’ll let someone else field your showdown, but I would go Yanni, too. But I actually did enjoy his album Keys to Imagination. Back when I was starting out learning synthesizer stuff and reading Keyboard magazine, I did find that album to be well-composed and ear-opening for me. A lot of the glassy DX7 (at least that’s what it sounds like to me) sounds didn’t age so well, but it was a pleasant, atmospheric album, with fun rhythms and catchy, if a bit simple and sometimes cheesy, melodies.
Richard Thompson. They’re both great, but man, can that guy work a guitar.
The Kinks or the Who?
I love both the Kinks and the Who, and that’s a real close one. I gotta go with the Kinks.
Weezer or Blink-182?
Weezer, by many light years.
Motörhead or the Stooges?
Motörhead. Because Lemmy is God!
Dead rapper faceoff:
Tupac or Biggie?
Guess I’d go with Tupac, he seemed to have more range than Biggie.
The Black Keys or The White Stripes?
White Stripes.
Miles Davis or John Coltrane?
To keep this thread from dying, I’ll say Miles Davis, even though I’m not a big jazz aficionado.
The Smiths or The Smithereens?
The Smithereens, by a mile. I love the Smithereens. They never got the recognition they deserve.
How about Dwight Yoakam or George Strait?
Dwight Yoakam is a slightly better musician and a MUCH better actor.
Blondie or the Cars?
Blondie by far. They had far more of an impact on music and culture than The Cars did.
Renaissance vs Gentle Giant?