Jolly well said, it's EVHs doing that tapping is now a common technique in rock music. It was done much earlier by classical and jazz guitarists, and some guys may have used it in rock music at the same time, but he made it big. Billy Gibbons used it as a kind of gimmic (he still does at live shows) but EVH really took of with it. And Eruption was, to my knowledge, the first solo in which tapping arpeggios appeared, or at least the first that ever became famous. So to call it underrated is a bit strange I think.