There is a ton of effort and focus on making female characters interesting in a majority of anime, however more often than not, we have a much blurred focus toward the male counterparts. The two reviews I've wrote both had this complaint in them and I'm wondering why the rememberable and interesting male protagonist has been push to the back seat.
Instead we have this generic nice guy, that all the girls happen to hover around. Having only one trait, niceness, that no other guy in the series has, makes it the driving focus for female fascination. Leaving an empty shell of a man with only one layer to him that every regular male claim to possess.
More Relatable
Some people, aka the producers of these anime, may argue that a generic male protagonist makes it easier for the viewer, mostly males, to substitute the character with themselves. This can be very true, but not everyone may want to insert themselves into the story, but rather just enjoy it as what it is, a story. With a story you need compelling characters to enhance the experience and make the viewer relate without having to plop ones self into the story to make it appealing.
Visual Novels Fault?
There is some blame to be pointed at Visual Novels with an anime adoption. Not really the Visual Novel itself, but the nature of it make sure the male is pretty transparent and not too out there. Since VNs want the player to be emerged into the story and not be hung up with the conflict of their own character and the character in the VN. Translating this to an anime really makes for a much flatter male compared to his female harem that seems to flock around him.
As a caveat, these descriptions of the flatter males only match visual novels that are based on getting the girl as a first and foremost goal, eroge if you will. Looking at a list of anime that have been adopted from VNs, that turned out excellent like, Steins;Gates, Clannad, and Shuffle, just to name a few.
Remember?
The consequence of mediocre males is the character only sit in memory for a very short amount of time and you forget them easily. Yuuki Rito, Kio Kakazu, Junichi Tachibana, these are three males in the center of a harem story and more than likely, not many people will remember which series they come from. Memorable characters are the end goal of most stories, if you can accomplish that, you have a pretty big problem.