text book it is 5 inches. 2 inches should be enough for sexual pleasure,but i don't know if 8 inches would be more pleasure then a "normal" size. the same reason that women get boob jobs,they think the other gender only likes big ones. i think porn has to do with a lot of men thinking theirs should be bigger. btw,i am a male and i'm not fascinated with the penis.
Because Man consider it that big penis has more power than short penis except this one a short penis can also have more power (timing to satisfy the woman) than long penis.