Yes but I don't act on it. I've only experienced it with crushes though, never in a relationship.
I don't believe it's about being "good enough", I believe it's pure lottery about the whims of the heart of another person. There's nothing you can do about it. They can pick someone else for whatever reason. Love/infatuation is pretty random.
So jealousy isn't about insecurity, it's simple the fear they will pick someone else. Or in the totally simplified way, it's discomfort from knowing someone else is getting what you want to be getting. And it can be as little as spending time with the person.