This amusing picture aside, it may not be as important.
Before you get the idea that I'm going to suggest willy-nilly inspecting the contents of guys' swimsuits (not a bad way to spend a Saturday afternoon), let me make this observation: Only a certain minimum size is needed; beyond that, it's how it is used.
Let's put it in perspective. Is it more satisfying to do it with a guy whose little soldier is five inches in length, but who lasts for fifteen minutes; or with a guy whose weapon is seven or eight inches, but who fires it in less than a minute? I think most women would know the answer.
In short, it's how it's played. And I mean foreplay. Make it last longer. If you give her multiple orgasms (or even one), you will be a hero. Putting it in is Act III; Acts I and II should not be neglected.
And there's more. In a recent issue of Maxim, they purported to interview 8,000 women. When given these choices, 86% preferred a guy who was not good in bed, but wonderful in all other ways, as opposed to 14% preferring the guy who was great in the sack but otherwise a bastard.