Harry/Luna seemed more likely in the books as time went on, moreso in the films. Ginny's silly crush always seemed to be something that would fade with time, and she did start dating others, then suddenly they're together? never made sense to me.
But Ron/Hermione was painfully obvious from the start, becoming more of a "get on with it already" stunted plot point until the final two books.
That's what I thought. And honestly, I also thought we just didn't see quieter moments with Ron and Hermione because we were focused on Harry. I mean, Ron and Hermione weren't with Harry 24/7.