…and is about as far from “spot on” as you can get.
Alone Again Or - UFO
Slightly spikier than the original but otherwise an effective Bowie tribute (right down to the oohs, aahs and grunts):
Bauhaus’ cover of Ziggy Stardust:
OB
Garth Brooks - Hard Luck Woman with the members of KISS backing him up.
String Cheese Incident does a pretty "spot on rendition of ***Sympathy for the Devil***
I’ve only read the title and the OP, and what first came in mind was Tom Petty’s cover of “I’ll Feel A Whole Lot Better” by the Byrds. It’s very close to the original, the only difference is between the 80s and 60s production. Even Petty (as always) sounds much like Roger McGuinn (I think Tom Petty, through some strange cosmological quirk, was really the love-child of McGuinn and Dylan). Please compare:
The Byrds - I’ll Feel A Whole Lot Better
Tom Petty - I’ll Feel A Whole Lot Better
Arguably the concept of “spot-on covers” carries the implicit assumption that the original is considered to be a stellar production, with the covers coming as close as possible to that level of achievement.
A cover becoming much more popular than the original would violate that assumption, yes.
I like that band. 
Great White does an amazing cover of Led Zeppelin’s Babe I’m gonna leave you.
From the OP:
I’m understanding this to mean how the original and the cover sound compared to each other, not a comparison of how successful they are.
4 Non Blondes cover of Misty Mountain Hop is great.
Wow. Sheryl Crow I want you Back sounds like excellent Karaoke impersonation over the original track The Bohemian Rhapsody one sounded like annoying karaoke over the original track. Hated it.
Billy Joel’s version of “Back In the USSR” matches the original in just about every way. You can see he’s having a blast playing it, too.
Spot on? I’m going to have to disagree. I liked it OK, but it’s nothing like the original. I could probably tell them apart listening under water.
I agree with this. It’s a nice cover but does not exude the terror and ferocity of the original. There’s nobody who solos like Keith Richards back in the day.
Naah, for that you want Laibach (not a candidate for this thread - Laibach make covers their own _ mean, seriously, that last one is this song, never mind what they did to One Vision…)
Heart does a great cover too. Ann’s voice is perfectly suited for the straight-ahead hard rock style of the original. Whereas Nancy’s backing vocals are the highlight of their cover of Battle of Evermore, Ann not doing the frail yet powerful thing as well as Plant (although not surpassing Sandy’s original.)
Oingo Boingo did a pretty good cover of I Am The Walrus.
Fountains of Wayne did a great cover of The Moody Blues’ Story In Your Eves
So did Styx.