I think the way Adam sings "Whole Lotta Love" just makes it an entirely different song.  I don't think you can really compare Zeppelin's version to his.  Zeppelin killed it in it's day, and it was a rock treasure.  Adam, however, took it to a whole new level and brought out the sexuality of the song in a way most of us can't even explain!  And his vocals….please….AMAZING!