If there are any bands/solo artists that everyone loves a song to, it would have to be either:
Michael Jackson
The Beatles
Elvis
Eric Clapton
Of those, I think Eric Clapton has the most varied body of work. I could see my grandmother possibly listening to some of his Unplugged album and liking it. Michael Jackson... you know you like at least one of his songs. The question is, how many age groups does he reach? I think quite a bit, but I don't know if it's enough. Songs like "Imagine" make the Beatles a possibility, but there were just too many drugs involved for EVERYONE to like their music. Plus, Stones fans hate Beatles fans, and vice versa, so they might be out just for that. Elvis would almost be a shoe-in if it weren't for his perception as a rebel. Many older folks wouldn't like him just because he was considered lude.
Either way, if there is a band EVERYONE likes at least one song from, it's got to be in that list.
Or maybe Toto. You don't fvck with Toto.... you just don't.
EDIT: Forgot about Billy Joel. That's possible. Doubtful, but possible.