The size doesn't matter to me. There are so many ways to be sexual besides penetration that are exciting...not that penetration isn't exciting! It is! I'm bi, and have had great sex with women with no penis involved whatsoever. I've also had sex with men without penetration, and it was very satisfying. Sex can be so much more than the old in & out.
All you really need is 8 because every female is only 8 inches deep. But thickness matters too! Although if a guy is small and admits to it he will probably have a good motion.
Not every woman is going to be comfortable with 8 inches.. Besides, if a man can make me cum from oral, he has skills.
Reading the posts in here its does seem that a guys skill and technique are more important than the size of his cock. Im just 7 inches which I think is about average, not massive, but I have never had any complaints about my love making because I use more than just my cock. Besides, my wife thinks im just the right size as I fit inside her perfectly. Any bigger would be too big for her!