Who say's covers are terrible?

I love BBC Radio 1's Live Lounge, because it gives us beauties like this


Little Mix covering Mumford and Sons - I Will Wait.

and this


The fabulously ginger Newton Falkner covering Payphone by Maroon 5.

I've also mentioned enough how much I smurfing love Birdy. But I'll link her again for any of you who haven't listened to her. (Why?!)



What are your favourite covers of songs? Also, on the other hand, what are some of the worst covers you've found?