The media usually portrays WoW as a "boy's game." That's not to say girls don't play too, of course -- just that the game is basically about qualities such as aggressiveness and violence, and our culture expects males to be interested in that sort of thing.
Whether such a designation is true or not, the "masculine equals violent" stereotype is very pervasive, and it is natural for many male players to begin the game with a powerful and intimidating character in mind. The player may imagine that his avatar is warm and kind-hearted inside, but outwardly, his character looks as though he could rip out your throat with a flick of his pinky finger.
But there are many men out there who don't like such exaggerated manliness in their characters, just as there are many women who don't want their character to look like a dainty barbie doll. Being a person isn't just about just one gender attribute, after all. Indeed, female characters in WoW can achieve a full range of human attributes in their appearance; they can look friendly and intelligent, yet lightning quick and deadly at the same time. However, the appearance of male characters is often so filled to the brim with "strength and honor" that there's not much room left for any other human quality.
Obviously, there are exceptions. Gnomish males certainly don't come across as intimidating so much as book-smart and goofy. They are great fun to play for laughs, but in general nobody takes a male gnome seriously. Blood elves and night elves, though often mentioned as the most effeminate of Warcraft males, are actually very imposing compared to most real-life men. If you put aside some of their hairstyles, emotes and dances (which can be entirely avoided if the player chooses), they have exaggerated muscles like all the rest, as well as their own special macho swagger.
Personally, I don't look very violent myself, nor do I even aspire to physically intimidate any other real person. While I have the utmost respect for men who must survive in dangerous circumstances, the ability to kill people or scare them off just isn't required of guys in my corner of the world these days, and "macho" is not a masculine trait I aspire to. Manliness, for me, means cooperating with others to achieve a particular goal, using language and communication to achieve what muscles and brawn used to do in ages past.
So in WoW I'd like to be able to play a spellcaster who looks more like myself; or perhaps a cheerful and wise old man with a long beard; or maybe even a troll who can stand up straight for more than 5 seconds. I don't want my male character to look wimpy, of course, but I don't want his skin to burst from excessive musculature either.
I remember trying to create a male night elf, and being unable to find any face that didn't scowl or grimace at me. Trying a human, I found all the faces to have small, stupid-looking eyes, wedge-shaped noses, and heads resting directly on their shoulders without any neck in between. Suffice it to say, I tried every male of every race and felt disappointed with my options -- sometimes it was the prevalence of scowling faces, other times it was the wrist-less arms the size of tree-trunks. With the Horde races, in particular, I was universally turned off by their hunched posture, facial deformities, or in the case of blood elves, the same arrogant swagger I dislike in night elves. Many men look at these characters and think "cool," but I look at them and think, "not my thing."
Of course it's entirely a matter of personal preference. I'm glad that many men (and women) have the option to play the macho character they enjoy: cool-looking, muscular, and ready to kick ass. I fully appreciate their sense of fun in playing that sort of role -- I just don't think it's suitable for me, and I wish I had some other options.
And why shouldn't I have options? As Elizabeth pointed out, female characters actually get a wide variety of visual appearance choices, from the tall and thin to short and stout, movie-star gorgeous to hideously grotesque. Sometimes, as in the case with female trolls, there's actually only one face which conforms to the prevailing standards of feminine beauty, but lots of faces with various grimaces and wrinkles for any woman who might be going after that special vicious look in her character. Yet, if these female characters were as limited as male characters are, they would all be variations on the barbie doll theme -- clearly designed for sex-appeal -- with the one possible exception of an anime cutsey girl with poofy pink ponytails.
To be fair, however, not everyone views these male characters the same way I do. When I asked female players which male characters they thought were attractive, I was most surprised when some of them mentioned that undead males looked "endearing" or "adorable." Tauren and draenei males are much easier for me to appreciate, in the case of players who see them more like gentle giants than intimidating monster-men. I have one male draenei character in particular who looks noble and graceful to me. His severe face and huge muscles don't bother me as much when I see them running along with a graceful gait, almost like a stag, as opposed to swaggering or wabbling about awkwardly as most males do.
Other players have created other exceptions to the imposing norm as well. Although I personally would not enjoy playing their characters, I nonetheless admire them as good male characters that break the macho mold. Some undead males, for example, look more scholarly than scary, and some people roleplay their blood elf males so shyly and timidly that I can almost forget their narcissistic posture.
In addition, men always have the option to play the opposite sex if that would fit the kind of character they have in mind better. Obviously female characters can't represent the peculiarities that makes us distinctly male, but they can portray almost any other characteristic we might want them to have, from friendliness to intelligence, silliness to bloodthirstiness. Often one can reach a visual balance with female characters that mixes several desired qualities in just one look.
Each person has their own vision of how they want their characters to look and feel, and it only makes sense that there should be as many options for different sorts of people as possible. What do you think of the male characters in WoW? Are you satisfied, or do you wish you could make some change?