rather like the cabbage soup diet, the "nice guy" sounds like a "good" idea, however both can be a burden on any specific long term, procreative goals. and let's face it, most guy's goals are to find a reasonably proportioned love object in order to liquor her up, and talk her into a lifetime soundtrack of "oh, for god's sake woman, would you please not leave THOSE underwear lying around for me to see."
the second cousin twice removed of "nice guy" is "just like my brother guy". again, these gentlemen will have a host of attractive females within arm's reach, but said females will also be trying to see if they can belch their lunchtime burrito far enough for "jlmb guy" to smell.
through the passage of time "nice guy" will typically move beyond the "maybe he's just gay" stage, and evolve into ken doll status; asexual. oddly enough "nice girl" is never left on the shelf, because honestly...there is no such thing. girls left on the shelf are collecting dust for a reason; their farts smell like boiled cabbage and they demand you accept them for all that they are.