From what I've commonly heard men complain about;
a) Mood swings that defy logical reasoning. Some men feel as though their wives intentionally look for things to argue about. It's as if being happy and co-existing (peacefully) bores them to death!
b) She's "perfect" as she is and (he) is a "work in progress"!
Whether the man is age 30, 40, 50, or beyond in her eyes it's a "miracle" he survived before (she) came into his life! He doesn't know how to boil water, make a bed, fold towels, or even load dishes in the dishwasher - "correctly" aka (her) way!
c) Instant demotion on her list of priorities
1. Children, 2. "Me time", 3. Immediate family, 4. Best friends for life. 5. husband (if there is any energy left)
d) Having sex is doing him a "favor".
It's something to be used on a reward/punishment basis. She never initiates it or makes him feel desirable. Over time she desexualizes the marriage where there is 0% eroticism. Oftentimes this leads a lot of the guys to venture onto porn sites and visit strip clubs. They want the "fantasy" of having a woman throw them self at them or make them the center of attention because they (never) get that treatment at home.
e) She treats him like a human ATM machine.
If he can't earn money quicker than she can spend it then he is a "loser". If she earns more than him she resents him for it. When it comes to money there is no "Us & We". There is only "You & Me". His money covers their expenses and her money is for doing whatever she wants.
I'm sure complaints would vary from marriage to marriage as well as what challenges the couple may be facing at a particular phase in their marriage.