Good question - I'm guessing a lot of men are concerned about this.   Basically, if you study the face shape and contours of good looking men there is quite a variety, isn't there.  But some basic differences do apply.

For example, men generally have a stronger jaw ( mandible) than women.  It's important with men's faces to preserve the strength and dominence of the mandible over the cheeks, or at least to balance them.  If the upper face starts to get wider than the lower, his face will look more feminine.  Also, a leaner more sculpted approach to the cheekbones is better because it speaks to the naturally lower body fat most men have.   If the contours of the cheeks themselves get too rounded it looks more feminine.   There are other things too but you can get the idea.  Hope this helps,  Dr. I