The "nice guy" is a stereotype or archetype describing an introverted adult male who seeks sexual attraction and romantic intimacy, but only finds cordial friendship and Platonic love. The "nice guy" sees himself as charming, sensitive, and attentive, but due to shyness, these traits go unnoticed to his intended love interests. The "nice guy" is constantly at odds with more aggressive, "Alpha male" suitors, hence the phrase, "nice guys finish last."
The "nice guy" is exemplified often in literature, film, television, and popular music. Often, stories are told from a first-person perspective.
On The Simpsons, Milhouse Van Houten is often cast as the "nice guy" seeking the attention of Lisa Simpson. In one instance, he tells himself, "if you do anything she wants, she's bound to respect you!"
"Nice Guy Syndrome"
"Nice Guy Syndrome" is also used to describe the frustration experienced by the "nice guy". In this case, the "nice guy" considers his condition to be little or no fault of his own; instead, he believes that women have poor taste and seek only his opposite, a hyper-masculine, hyper-aggressive ideal man.
William Sheldon's currently discredited somatotype theory stated that many of the personality and physical traits associated with "nice guys" were linked. Such men were of the ectomorph type. Some have linked this type to low levels of testosterone.
In No More Mr. Nice Guy, Dr. Robert A. Glover describes the "Nice Guy Syndrome." Glover writes with a slightly masculist perspective from his experience as a therapist. He views the Nice Guy Syndrome as a problem to be cured. Unlike some self-described nice guys, he does not ascribe the supposed female rejection of "nice guys" to poor female taste. He believes "nice guys" to be troubled by clinical depression, low self-esteem, internalized toxic shame, and confusion over roles, and that these issues make "nice guys" less attractive to women.
Biological science and evolutionary psychology have explained a possible evolutionary role for the "nice guys" of this theory. Humans can act like the cuckoo - the eggs are fertilized by one father, but another bird raises the children.
Studies have found that ovulating women prefer men with testosterone-influenced characteristics they consider "rough", while women in other parts of their menstrual cycle prefer men that look like "nice guys". Nasty types are preferred for short term flings (primarily involving sex), while "nice guys" are preferred for long term relationships (which often include child rearing).   .