Men can be just as jealous as women. It just manifests itself differently.
Speaking as a (Mystery) man, jealously for men never seems to be as all-encompassing as the jealousy that many women seem to experience. That is to say, men might be jealous of someone's job, or someone's love life, or someone's athletic ability. Rarely are men jealous of the whole person, as women seem to be.
It's not that men are more confident. They just instinctually try to come up with some kind of self-affirming truth when they compare themselves to someone else. Something like "He may be stronger, but I'm faster." Or "He may have a better job, but I've got a hotter girlfriend."
Women, by contrast, don't seem to do that. You're much more inclined to hear a woman say "she's perfect" than a man. That difference makes it seem like women are constantly jealous while men are constantly self-assured even though that isn't remotely the case.
Men can be just as insecure and jealous. But something deep in our psyche prevents us from getting fully swallowed by it. I suppose that makes us lucky.
Ladies, what are your thoughts? I'm speaking in generalizations, of course, but is that how you generally see this issue too?