First of all...
Hip-hop>>>> Metal if anything. Oh wait, it's all subjective anyway. Either statement of one being superior is ridiculous.
Crazy Train is a brilliant pop song, worthy of The Beatles.
I don't see what's so wrong about sampling songs. Most people know that it's not their song originally. Unlike that stupid band Jet and the way they ripped off Lust for Life.
Great artists can also use sampling, often to a great effect. Some have said that the Beatles song "All You Need is Love" is sort of pre-sampling, as even though they played the french national anthem opening, it was used in the same way that sampling is. There often can be quite a bit of creativity to it.
Borrowing riffs has also been around quite a bit. There are a ton of early rock songs that use the Chuck Berry riff.
To say that most forms of electronic music are derived from hip-hop is not entirely true.
Electronic music has been around since the 60's. Again, The Beatles did stuff in early electronic music.
Hip-hop wasn't around until the late 70's, with the first rap song ever recorded, Rapper's Delight by The Sugarhill Gang, released in 1979.
Electronic music and hip-hop since then have influenced each other. Indeed, pretty much all modern forms of electronic music are hip-hop influenced.
It's not the side effects of cocaine, so then I'm thinking that it must be love