I was watching the poorly-received Over Her Dead Body (2008) the other night, (Rotten Tomatoes = 14%) and enjoying it, when, along toward the middle of the movie, Paul Rudd and Lake Bell realize that they're in love, and smooch. Then, pulling back, Rudd makes a little joke about it. Ok, I understand that there is such a thing as a "script," and that in this romantic comedy, the protagonists are keeping it light, but still... After Bell lays one on him, in a perfect world, wouldn't Rudd have a few more stars in his eyes? So it occured to me that his star power, so cool here, maybe was overmatching Lake's, whereas if he tried that with Angelina Jolie, say, he'd have looked like a schmoe. Could it be that when we talk about the chemistry between a man and a woman in a romantic movie, we're just comparing their relative star powers? If the luminesences match, the kiss works; otherwise, it doesn't? So that Tom Hanks can't give or receive a good smooch in his movies because he's too big, starwise, for his leading ladies? The Fiennes brothers are good smoochers because they consistently hook up with medium-level female stars? Or how about Ryan Gosling and Rachel McAdams in The Notebook (2004) - there's a star-power match.
Requires further research.