Rock Candy
Rock 'n' Roll Doctor
We all know when this happens, a cover of a song far exceeds the original in notability/popularity to the point that it becomes the "original" version in people's eyes. Any examples that spring to mind? Up to two at a time, if you'd be so kind 
The Loner
The original: Cozy Powell w/ Clem Clempson
More famous cover: Gary Moore
Interestingly, Moore played on Cozy Powell's Over the Top album, but not on "The Loner". When Moore did his own version in 1987, he fiddled around with the arrangement a bit, which earned him a co-write credit.
Since You Been Gone
The original: Russ Ballard
More famous cover: Rainbow (Albeit Blackmore supposedly heard Clout's cover first)
The Loner
The original: Cozy Powell w/ Clem Clempson
More famous cover: Gary Moore
Interestingly, Moore played on Cozy Powell's Over the Top album, but not on "The Loner". When Moore did his own version in 1987, he fiddled around with the arrangement a bit, which earned him a co-write credit.
Since You Been Gone
The original: Russ Ballard
More famous cover: Rainbow (Albeit Blackmore supposedly heard Clout's cover first)