You're gonna be bothered by how cool I am.

A lot of my thoughts echo what peachespig said (big surprise, I know ;) ). For me, R/Hr and H/G really are two parts of the same whole: OBHWF all the way baby!

While H/G is my OTP, I genuinely love R/Hr as single/separate ship as well. From a storytelling perspective, I do think R/Hr was a more prominent ship as a subplot. It had internal conflict that needed to be resolved in order for the characters to complete their primary arcs and to be the best supporters to the protagonist that they could. H/G is very important in the overall outcome of the coming-of-age plot but it was not featured in the same way, for as long a time, etc. And there was more opportunity for readers to become invested in each of the halves of the whole relationship. Many of us connected very strongly to Ginny even prior to OotP, but I can't argue that we know her as well as we know Ron and Hermione and I don't think JKR would try to say that we do.

However, I also have to say that calling R/Hr THE romance of the series is not quite right and I don't think a lot of the people who've said that mean it quite that way anyway. From my perspective, I have to admit that I might not be as fond of R/Hr if Harry did not get together with Ginny, because that would leave him kind of "out in the cold" IMO (unless he had died and stayed dead).