Everyone knows that men are commitment phobes and women are faithless. Well, that may or may not have any basis in reality, but it's the cliche. I had a flash on why many have a lower opinion of the opposite sex' relationship potential than is real.
Most of us only end up in a small number of semi-permanent relationships that last more than a year or two, unless you are Elizabeth Taylor. So you have one, two, or three men or women with whom things really worked out for a few years.
But most people dated before the semi-permanent relationships and since they didn't last a long time, there were a bunch of them. If you date six guys and break up with them, and then have a real click with guy number 7, well, look at the count. Six men were lame, one good. In fact, you stop looking as soon as you get the good one (well, you are supposed to), which means you never encounter the other good ones. It's complete sample bias.
Or maybe most men are skirt-chasing, womanizing, juvenile, sports-obsessed idiots. I'm good with whichever explanation.