Other men fucking wife.
I think I understand what you are feeling. I've been there myself. I know the mixed feelings of knowing that another guy is having fantasies about fucking my wife. It is at the same time both the most frightening and exciting thing you can imagine.
Any guy who is really "into" his wife, and who is really attached to her pussy has to constantly worry that some other guy will come along who will "steal" her away. The only way a husband can survive such fears is to tell himself that no matter what happens, he will still want to fuck his wife and that her pussy will still be the center of his sexual universe.
As for another man saying "I'd like to fuck your wife!", you can either take it is an insult to you, or a compliment to her. As a husband who has heard these exact words several times, I can tell you that it excites the hell out of me to know that some other guy is wanting to stick his dick in MY pussy!
I'll tell you one that is even hotter. That is to say to some guy "How would you like to fuck my wife?" The look on the other guy's face is priceless as he hears you even suggest the remote possibility of him getting to fuck YOUR wife!
Most guys will think you are joking and will ask "Are you serious? Would you let me fuck your wife?" That leaves you to say the words that any wife-sharing husband loves to say to another man, "Sure, you can fuck my wife! She's a great little cunt! You'll love sticking your dick up her hot hole!"
Those are the "three little words" that will excite any husband, once he has the balls to say them: "Fuck My Wife!"