Well, there is nothing wrong in some jealousy you feel: it is a compliment for each of us. Ayway i think you have to be careful, because this jealousy should not interfere with you private and sex life.
Again, even though personally i could never have sex with your wife (i am too in love with my gf and i respect marriage), nothing wrong with your fantasies, as long as your wife shares them.
Take care, mate!