The fact is most people (men/women)are not happy or totally satisfied
with their life. So, if you establish this as base, the notion that
married men (or women) are not happy would be correct. However, the
simple fact that single men/women continue to seek longterm
relationship even after so many failed attempts is a good indication
that single men/women too are not happy with their life. In fact,
there was another study (too lazy to look it up - sorry) that said
unmarried people (single) are more stressful than their counterparts
due to social pressure/expectations.

Peace,
HK