Sure, some rap and hip-hop qualifies as art as much as any other form. There is really bad music in every genre, so why should rap be any different?
And yes, there are 15+ year old rap albums/cd's that I still play -Digable Planets, NWA, Public Enemy, etc.
Do I consider these recordings as timeless as some Coltrane, Miles, or Nat King Cole, etc? No, but I don't put the Eagles, Police, or Elton John in that category, either. Zep, yes, Eagles, no.
While I'm at it, plenty of rock artist made it big ripping off others and not giving credit. Do you really think Robert Plant thought up "Squeeze the lemon 'til the juice runs down my leg"?