mmm, I think most guys want a loyal wife they can look after and be proud to be with.... where as a girl is looking for someone to look after her..... and shell keep an open eye for anyone who could do a better job of it than her man
(it sounds oldfassioned... but i think it still applies)
p.s. were talking real relationships here, not short ones
edit:
i think also part of the trouble is that in general its MUCH easier for a woman to find a sexual partner, because us men are dogs
yeah, the vast majority of juys i know go out with the first girl that looks at them twice and gives them half a chance...
but tbh, Id rather be single than with 95% of girls (unless im horny that is)