Can we say Grave Digger just humiliates Metallica and Judas Priest?

They are good. But they are around in part because of said bands. They fed off of thrash which Metallica helped create. And Judas Priest helped usher in speed and heavy metal. But they helped create what they are today. On their own.

Well, considering that only a fraction of the people out there have ever even heard of the first band you mentioned, I would say no. In fact, the members of this band you speak of, this "Grave Digger", would likely spunk into their tighty whities if they knew that someone on this planet actually mentioned their shite fecking band in the same sentence as Metallica and Priest. "Grave Digger" sounds like the name of a monster truck in a demolition derby "SUNDAY, SUNDAY, SUNDAY - GRAAAVE DIIIGGER..." Hahahaha what a retarded fecking name. No one could take a band with a name like that seriously. You're hilarious, man. Next you'll be telling us that GWAR is better than Iron Maiden and Manowar is better than Slayer. What a fecking knob.

Fancy work of fiction, dude

Nooo

No! Just because a musical artist (of any type) has a "new sound" (or in some people's eyes) is more skilled than an earlier musical artist, it doesn't erase the greatness or popularity of the classic artist! Those bands and artists are legendary and influential in a way that will never be eclipsed by a newer artist...no matter how good or popular they are! The elder artist's legend is already set in stone! Chances are that bands such as "Grave Digger" (whoever they are) will fade into obscurity while the legend and influence of pioneering bands like Metallica and Judas Priest will live on!