I could have picked all of them.
But, I guess I'd have to go with "Don't Stop". I remember that song was on the radio all the time all that summer & it did come closest to #1. It's such a terrific upbeat song. "Little Lies" would be my second choice, extremely catchy, pure perfect pop. But my favorite song of her singles is "You Make Loving Fun". The most underrated song of her singles is "Think About Me". That song should have charted much higher.
Technically, Chris had four #1 singles-"Got A Hold On Me", "Little Lies", "Everywhere" & "As Long As You Follow"(on the Adult Contemporary chart).
I also agree about "Friend". That was one of her best singles ever.