General Statement about covers

When covers are recorded, I feel that they should offer something new. That's possible, even if the band covering the song and the original artist are from the same genre. Opeth's cover of "Circle of the Tyrants," for example -- they added parts to the song and made it sound more like Opeth. At the same time, the integrity of the song remains.

It can also be interesting for bands to cover songs live on occasion -- I consider it a tribute to the original artist (usually one that inspired the band), and can be nice if performed well.
 
Well covers are very essentially for new bands who have no material written to perform. At band practice its always good to have a few songs in reserve that you can jam to just for the hell of it. When playing a cover live... I think it's good fun. It's always good to see how well some guys can re-intepret or match an already existing metal song... it doesn't need to be drastically different in its approach to impress me in live situations.

When it comes to recording covers for albums, compilations or what not, it's obvious that the band have more time to work with their interpretation and alot of bands do change the song they're covering quite a bit. Some do it well, some don't and that's how it is.

But I really don't understand why you have some huge standard of greatness for covers to adhere to. In practice they are just for fun, and I think all serious artists know that.. it's not like there is a universal competition to see whether a cover can be made to sound better than the original. That's where original music comes from.