Certain groups fall into that category, I believe. Groups or singers with a signature sound, don't seem to cover too well...Led Zep, Beatles, Queen, ect. There's quite a few when you think about it.

Couple of Dylan covers, Mr Tambourine Man by the Byrds and All Along the Watchtower by Hendrix were good. On the flipside, I find U2's cover of All Along the Watchtower pretty bad.

Half of communication is listening. You can't listen with your mouth.