there's conflicting evidence about whether gay men are happier than straight ones or not. some studies suggest they are, some other studies suggest they are more prone to depression and even suicide. but their distress can be ascribed to society still not accepting or tolerating homosexuality.
If homosexuality was fully normalized and not seen as a big deal or problematic as it still is now I would guess gay men would be happier than straight ones for two reasons:

  1. they can easily have a more intense and fullfilling sex life when it comes to casual sex because they don't have to struggle nearly as much to negotiate their attractivity to another person as straight guys have to do with women except maybe for top alphas. having a varied and intense sex life is a dream for a lot of us men.
  2. they don't have to act tough or stoic most of the time like straight guys do to win women's affection and companionship. being tough and stoic is a basic requirement that women expect from men in a relationship.
    I imagine that even in a gay couple you have one person who plays the man's part and the other person who plays a more feminine part but the roles are less strict and more blurried.