There are ladies that prefer 8 inches, and ladies that prefer 4.
Some will not feel it deep enough, some others will say it hurts because it's too deep.
Just...make sure you and your partner find a way to make good use of whatever you've got. Select poses that will set you on the right depth, do magic with other sorts of penetrative and non-penetrative sex, and just listen to each other's bodies.
Also, to everyone who goes with "big dick = alpha" shit, you're both wrong and make it hard to unfuck some guys' minds on what makes them good for sex.
It's the other way round! A penis is more a derivative of a clit. That's why that line along the balls exists: everything started out closer to a vulva, and that line is where the proto labia fused.
Neither is derivative of the other, they both grow from a common source. It's like saying humans evolved from chimps, it's not true, both came from a common ancestor that itself is neither chimp or human.
From the perspective of human fetal development, the structures will develop into a vulva, vagina, uterus, and ovaries unless the fetus has its own DHEAS and testosterone to alter the growth pattern. There are plenty of people that have XY chromosomes that have entirely female genitalia because their testosterone receptors are broken.