Maybe not the best cover ever but every time e metal band covers a pop song and kicks it up a notch, I smile inside.

Disturbed covers Genesis - Land of Confusion

Scorpions do The Who - I can't Explain

This one is not an improvement by any means but worth a look in the "kick it up a notch" category.
Korn does Pink Floyd's Another Brick in the Wall

And if you suffered through that one, I'll make it up to you with a very interesting variant of a Beatles song. Very differnt but good in a dark sort of way.
A perfect Circle does Imagine


And because i hated Tears for Fears almost as much as I hated Wham back in the day, I do literally have to "Shout" and smile when I hear Disturbed do this one.
Disturbed piledrives Tears for Fears with this version of Shout

With great power comes Awesome irresponsibility.