It depends on my mom's mood.
She really likes Selah (a Christian group), Carpenters, The Commodores, The Beatles, many others (including a little Michael and J5). But it depends on her mood overall. And I like everything she does.
My dad is classic rock through and through. I'm not sure who his top 3 are. But, he really likes Led Zeppelin, The Beatles (later years for some odd reason), Lynyrd Skynyrd, Paul McCartney and Wings, Charlie Daniels Band, AC/DC, Black Sabbath, etc. And, of course, I love everything he does, too!
My grandma really likes Dean Martin, Neil Diamond, and the McGuire Sisters!! (Love them all, too!) My high school principal used to live next door to the McGuire Sisters.