Says you. When they first emerged on the scene, the adults at the time said the Beatles, The Who and the Stones were all crap and could never be compared to Pat Boone or Dean Martin. Do you really think that 50 year old adults really flocked to see Led Zepplin?
Who is talking about adults? My kids think gansta rap sucks and so do all of their friends.
For one thing, even though parents frowned on it, the latter music was performed on instruments and had singing. Rap is chopped up bits of somebody elses performances, and they talk, shout really.
Rap music of today is more closely aligned to Hitler's harangues of hatred from the 1930s than it is to any kind of music that has ever existed in the world or ever will.
LZ still gets airplay today, as do the Beatles and Rolling Stones.
Once Hip Hop "hits" fall out of favor, they're never seen again.
If longevity is any basis for the assessment of music, Rap comes up short, however popular the genre might be.