No, that's a myth. Chemistry is not like magic, there's always a reason for things. Here's how to figure it out. Just ask yourself the question.
Ask yourself: why do certain people have chemistry and others don't? There must be a reason. What could it be? It's because certain people's natural screen qualities compliment each other, opposites usually work well, but it doesn't have to be, just different but in a complimentary way.
That's why Billy Crystal and Meg Ryan worked so well together. Meg Ryan is soft and sweet and Billy Crystal was more sharp and cynical, yet also likable with the same softness under the surface. That's why Tom Hanks works with Meg Ryan, too, he has that same sharpness with softness underneath. This is just a quick example, but my point is that "chemistry" has a source and it has reason and if you're capable of perceiving and understanding actors' screen qualities, you can predict who will have chemistry. Most people don't perceive actors' screen qualities, they just look at them and go, "I like them," or "I don't like them," but they don't understand what vibe that actor is really giving off, especially beyond the surface.
If you have this ability to perceive, you can talk about potential chemistry intelligently. You may not always be right, but you'll have a pretty good gauge. And I'm telling you, with Henry Cavill as Superman, with someone that polished and regal and truly otherworldly, the person who will have chemistry with him is a woman who is REAL, not an icy femme fatale or actress who's also a supermodel in her spare time. Just look at Chris Reeve and Margot Kidder. Does everything that I'm saying apply? Yes. Does it work? Yes. If Olivia Wilde is cast, she will not have chemistry with Cavill. Neither will Mila Kunis or anyone in that mold. It's about certain molds "clicking." With Cavill, you need someone who is real and likable, and has a sharp intelligence, but also a girlish side, so that she's attracted to Superman's strength and power and moral compass (because she has all those traits herself), but so she's also in awe of him like a school girl with a crush on the captain of the football team.
You can save this post of mine and see if I'm right. When whoever gets cast as Lois gets cast and if she's good with Cavill or not, apply her to my set of criteria and tell me if I know what I'm talking about.
I predicted Ledger far surpassing Jack Nicholson and giving a career performance as the Joker and everyone thought I was crazy, busy saying, "What? the guy from 10 Things I Hate About You?" I predicted Henry Cavill getting cast as Superman when everyone said he's already been disqualified for a mountain of reasons because I could tell his career was in the right place and he had the right qualities for it and everyone laughed at me and called me a "troll." And I predicted the failure of Brandon Routh as Superman saying that he was a bad actor and didn't have charisma and that was before the movie came out. What are people saying about him now? How did I know these things were going to happen? Because I know actors. I can tell how they're going to be before they be. I'm a movie director, it's my job, I have to go out on a limb and cast actors in roles before they've already played the role and *gasp* predict how they're going to do and my career depends on it, so I've gotten pretty good at it over the years.
So you can take my words to the bank. You need an actress with the regal Cavill who's real, not a male-fantasy, not otherworldly, not unattainable, or else they won't have chemistry and their romance won't be romantic.
No such thing. If he can't make the ladies swoon, then he's no Superman 
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