My close friend fucked my wife for years, with my blessing. He knew from the locker room and from the nude beach that his cock dwarfed mine, as his was huge, and mine is average.
The thought of his big cock fucking my wife got me very excited, and still does, even though they are no longer able to get together because of geography. He never gave off the slightest vibe that he considered himself the alpha male and me inferior. He has always respected the relationship that my wife and I have, and sharing her with him has been one of the most positive and sexually gratifying parts of my life.
It was male bonding to the max, even though, unlike me, he is straight and we never had MMF sex. I am proud to have been man enough to not feel threatened for my friend fucking the one woman -- my wife -- whom he craved more than all those other women he could easily have had.
To this day, the experience of fucking my wife and cumming inside her is enhanced considerably by the knowledge that his cock has been inside that cunt so many times and that the two of them had such a loving and sexually charged relationship.