There is no such thing as an “Ideal” penis size. It seems most guys still haven’t learnt that women are inconsistent and changeable by definition.
From what I read, most women seem to have had “a big one”. Way more than statistics would suggest likely.
I am pretty sure most women would like to “try a big one” at least once, which is why hung guys probably have much more success scoring as they are a statistical minority. However, I doubt most women can judge size accurately anyway.
It also depends on whether she is ovulating and horny or at some other stage of the cycle. Also many post-menopausal women become less elastic down there, which means less girth becomes a requirement. Yet another factor is that erection during sex is often variable anyway.
Another thing often implied is that big guys don’t know how to please women as well, which seems to be a kind of sizeist remark (but gives PEers an advantage)
If you really must have some number, there seemed to be some consensus in another thread that 7.5 x 5.5 is the most practical all-round size.
If anything, the general rule seems to be that big may get more sex but average gets more quality relationships.