GNR were a great band, and Axl's voice suited there music well but he would absolutely murder Queen songs, they are very different styles of music.
Paul Rogers = not as good as Freddie, but better than most
Actually like many I've always thought George Michael would be a good replacement (since he was such a fan of the band and Freddie especially). But now that I'm going to see them at the Hollywood Bowl, I'm kind of glad it's Paul because I think he'll be better at the heavier stuff...I can't picture George Michael on stage singing TYMD for instance :)