4 girls is the most balanced.
The more girls the more forgettable and interchangeable they are.
At that point there just one night stands instead of a harem.
As many as possible really, it's more a question of time/effort limitations
This is the main issu.
One of the appealing thing about superpowered is the sheer amount of custom designed girls.
Ever single one with there own personality, clothing style, and looks.
But your ability to interact with them is limited.
Likewise some games have random generated girls who all become interchangable and with the same personality.
A good harem game in my opion is less about the amount of girls and more about the girls being more then just dickwarmers you use randomly.
Slaves tent to be better for find, fuck, forget.
Harems games i expect a bigger focus on who the girls are then how many there are.
I rather have a large game with hunderds of woman each with there own personalty, clothing style and looks but realisticly speaking that is too much work for to little reward.
Its better to have a small group of well thought out harem woman then an army of woman who all act the same, look similier and dress similer.
Now make no mistake.
There is a certian joy into dehumanizing slave.
Making them all dress the same, have the same hair, name them the same.
Destroying every induvality there suppose to have.
But that is about slave management games.
When it comes to harem i want people i can corrupt, manipulate and control.
Keyword people aka having a mind and personality of there own and not just stats to manage.