I think it's an interesting question. My first thoughts were the Beatles and Elvis, but it's hard to say. They've stood the short term test of time, but 250 years is a long time. The only things that seem to have lasted are masterpiece works and folk/kid songs. Who knows what "popular music" from that time have faded away.
What if people are singing "I wish I was an Oscar Mayer wiener..." in 250 years? The stuff that is burned into the cultural psyche.