This question is a little different, but I'm curious. Have you ever rejected a query, proposal, or manuscript, but much later down the line saw the book on the shelves, selling like mad, and thought, "Damn."
I've certainly seen projects I've not taken on go on to be repped and sold, but I don't think I've passed on anything like 50 Shades of Gray, or Harry Potter, or even Lee Child.
On the other hand, I'm probably not the right person to answer this question because I don't really keep track of things I've passed on. It's entirely possible I have passed on things that went on to do well, and I'm just unaware of them.
I do know that editors are a bit more keenly aware of what they were offered [and not.] I've sold a couple books on very exclusive submission, only to have other editors call to ask if someone else at the publisher had seen the book and passed.
It's easy to have a million regrets in this business, but it's critical for morale to keep them at bay. My focus is on what's coming up that will knock your sox off, not what I missed two years ago.