A common misconception about the Mary Sue label is that male characters are exempt from it. This kind of thinking is what allows the Marty Stu to run rampant, in both fan and professional fiction. The Marty Stu has persisted in fiction for at least as long as the Mary Sue, despite the latter being identified and troped about first.
Variations of the Marty Stu exist, each expressing different ideas of what constitutes "male perfection" (and by extension "female perfection"), and go by many names, including Gary Stu, Larry Stu, Mary Joe, and Marty Sam. However you identify him, all the rules that apply to Mary Sue apply to this male equivalent.
The Mary Sue radiates a soft glow of purity and beauty into the narrative around her and serves as the love interest to other characters. She may or may not be an Action Girl, but traditional femininity is always a key part of her character. The Marty Stu, on the other hand, always takes an active role in dramatic events, through pure testosterone-filled action if he is a nigh-invincible manly man, or through massive breakthroughs in science and technology if he is a super-genius. Whether the Marty Stu is of an intellectual bent or not, he always takes an active role in dramatic events; to not do so would be considered "unmanly and imperfect".
While once upon a time the Mary Sue would never be an active element, as that was considered too masculine for a "paragon of female perfection", she has since been freed to actively participate in the plot. In contrast, the Marty Stu is almost never seen taking on his sister's old Purity Sue role; rarely is he depicted as a passive motivator of others through his purity, beauty and helplessness. When he is, it is almost exclusively as a weakened Possession Sue in a Yaoi fanfic.
Marty Stu is devastatingly handsome (or if not, possessed of a strange, saturnine magnetism) and desired by all significant women, yes, but romance is not likely to be the main dish. He's an unstoppable fighter, a rogue agent, a fearless freedom fighter, a master of disguise. However, as times have changed, just as Mary's acquired a bratty temper, Marty's had the occasional opportunity to show his softer side.
Once upon a time, Mary Sues were noticed and hated to a much greater degree than Marty Stus. It was almost as if male characters were forgiven for being implausibly plastic because they upheld stereotypically male virtues such as toughness, courage, and heterosexual promiscuity. And while men have finally begun to demand more realistic protagonists, making Marty Stu somewhat less acceptable it is still clear that Marty Stus still get passes far more frequently than Mary Sues resulting in quite a fair number of male canon sues who conversely are praised rather than criticized. Part of this may be due to Most Fanfic Writers Are Girls as well as Most Writers Are Male. Both female and male writers for analogous but different reasons tend to like such characters.
See also The Ace, which is usually made as a nod to the less realistic male characters of old and plays it as a supporting character for comedic purposes.
Common Marty Stu Traits
As far as their traits go, Marty Stu incorporates most of the Common Mary Sue Traits while having quite a few general trends to differentiate him. While the textbook Mary Sue is generally made as a pseudo-realistic ideal of feminine perfection, Marty Stu tends towards taking the Rule of Cool TO THE EXTREME!! Due in part to the Double Standard, Marty tends to be less of an emotional cornerstone and more just an embodiment of pure physical and mental awesome (ala God Mode Sue). He's the type that tends to be stronger than The Incredible Hulk, faster than Sonic the Hedgehog, and have more MP than God.
Marty also generally doesn't have the sort of purity common in Mary (although it's not unheard of). Instead, he tends more towards the Darker and Edgier path, with a tragic and very personal backstory being the order of the day. Whereas Mary would use this to emphasize just how special she truly is, Marty uses it for the sake of brooding. No doubt much of the recent popularity of this character trait owes credit to Batman and Wolverine (debatably also good examples of Marty Stu themselves, in the wrong hands), but there's no indication that it only started with those characters.
Obviously, neither of these traits are exclusive to Marty. There exist plenty of God Mode and Sympathetic Sues, but in sheer percentage, it's more common on Marty. Since All Girls Want Bad Boys, after all, increasing the Badass potential of a character has the secondary effect of making him more attractive to women without having to sacrifice any capability. Sometimes, this attitude goes just a little too far and creates Jerk Sue.
Just like the Always Male category on this Wiki, there's painfully little that Marty does that Mary doesn't, generally being limited to sexuality-related things. Nonetheless, here's the little bitty list of exclusive Marty Stu traits:
- Perma-Stubble. Nothing like the scratchy beginnings of a beard to emphasize that no, testosterone isn't in any sort of short supply for him. Actual beards are surprisingly rare.
- Make him big and muscular. Even in professions where he does little physical work and shouldn't have time to train to be an Olympic weightlifter. While there's nothing preventing Mary from doing this as well, you won't see it happen very often (although there are some examples) because being muscular takes away from feminine charm in the eyes of most writers (if she needs to be strong, she'll often just practice Waif Fu).
- Conversely, make him lean and streamlined, as is common with more romantic heroes; the female audience prefers the dancer's build with swimmer's torso. Overly conspicuous muscles are avoided for pretty much the same reason as they are with the Distaff Counterpart: because they detract from physical grace.
- Lots of sex with lots of women (or men, or both, or even more than that). Sometimes up to the point of Marry Them All, completely out of place with the setting. Girls can do this too, but thanks to the Double Standard it's usually considered a more Stuish trait.
- Though, it does seem like there's a lot more Mary Sues than Marty Stus out there...