I would agree that Queens songs have more 'mass market' appeal and therefore the lyrics are likely to be better known (and thus sung along with) than Led Zeps.
However, for you to state that the singer isn't as important is frankly ridiculous. Freddie Mercury WAS Queen and he is irreplaceable to those of us who were brought up on Queens music from the early days until his demise. No matter how good Paul Rogers may be as a frontman he ain't no Freddie and the band isn't Queen just because he sings Queens songs.
You then mention it is all about performance. Have you never seen Freddie 'milking' a crowd? Held them in the palm of his hand he did - he was that good.
All IMHO of course :icon_wink