I was way too big a geek in the '70's to listen to pop music radio. And actually, I'm still too big of a geek to listen to it today. That said, I must admit to being rather enamored of a few artists of the seventies. I rather enjoy the musical stylings of Frank Zappa, Randy Newman, Warren Zevon and Steely Dan quite a bit.
But I was more into Edgard Varese, Anton Webern, Arnold Schoenberg and Roger Sessions. God, I was such a nerd...I remember special ordering an LP of Sessions Second Symphony from Japan, and waiting five or six months for it to arrive. I really liked the album, even if it was in mono, and played it constantly for over a year.
So my favorite hit of the seventies was actually Roger Sessions' Second Symphony.