I don't know who Mike He is. I didn't attempt to watch summer fever nor inborn pair (just cause it felt so so wrong.. It didn't seem right.)
But i've seen one youtube video comparing inborn pair and love now "intimate" scene.
In my opinion, There are 2 main factors.
1. Guy.... Chris was just kissing Annie, just for the sake of it. To me it was like he was just ravaging on annie. While george, was not in a rush. He took his time and also waited for Annie. I especially like those subtle forehead bumps.
2. Annie. The huge difference, annie was reciprocating geo's kisses (mainly because, geo gave her time to). Unlike in inborn pair kiss, it was more like a one-sided kiss. Chris was doing all the job done.