Humans Are Leaders

"Look, little girl. When you want a problem shot, ask a turian. When you want a problem talked to death, ask an asari. When you want a new problem, ask a salarian. When you want a problem fixed, ask a human."

—Commander Shepard (Renegade option), Mass Effect 2

A specific permutation of Humans Are Special.

In general, wherever humans coexist with other races, the humans tend to be the dominant or driving force in whatever effort they're involved in. They're the ones who tend to be the guys behind creating The Alliance and holding it together, the ones coming up with most of the plans on how to thwart The Empire, or—in somewhat darker settings—the ones able to manipulate other races into doing their bidding for them.

While this trope can be found in all forms of media, it's particularly prevalent in video games, where it usually translates into some kind of bonus to diplomacy.

Contrast with Humans Are Morons. Mighty Whitey is an earthbound sister trope. Probably influenced by Most Writers Are Human as well.

Examples of Humans Are Leaders include:

Film

In Star Wars, the Rebellion against The Empire was mostly started by humans. Alien Rebels only appeared in the later episodes, though the Star Wars Expanded Universe gives alien races more importance in the start of the Rebellion. Also, in the prequels, the two Supreme Chancellors we see are humans.
- The EU actually does make a point, in the X Wing Series while handling Fantastic Racism, that in the beginning, and around the battle of Yavin, humans were the ones who were putting themselves on the line, especially considering that the Death Star was functioning. There were nonhumans at various levels contributing, but at the time it was predominantly a human effort, and only after the success at Yavin did others start to support the movement more openly.
  - Admiral Ackbar, for example, was openly part of the Rebel Alliance and brought some resources and some of his people with him, but he didn't become a major element of Alliance High Command until after Yavin, after winning some smaller victories and gaining the support of the Mon Calamari.
  - It should be noted that the Rebellion would likely never succeed without Ackbar and the Mon Calamari ships, which are the most capable of Rebel ships in terms of having a snowball's chance in hell of surviving a slugfest with an Imperial Star Destroyer.
- Though this isn't terribly unexpected since humans were always the majority species in the Star Wars galaxy. And it's worth noting that humans started and comprised the majority of the Empire, too.

Literature

In E. E. "Doc" Smith's Lensman stories the humans of ~~Earth~~ Tellus led and provided most of the membership of the Galactic Patrol, even though other races were involved.
In John D. MacDonald's Ballroom of the Skies, the galactic government deliberately keeps Earth impoverished and war-torn ... because that toughens Earthpeople spiritually to the point that they make good recruits — to run the galactic government.
In one of Gordon R. Dickson's stories, the aliens of a far distant planet are extremely glad to see humans jetting around again, taking charge of things—because none of them really want all that trouble.

Live Action TV

In Star Trek, humans are largely implied to be the driving force of The Federation, particularly considering that its headquarters is on Earth and most Starfleet officers (that we've seen) are human.
- Starfleet is to the Federation what the Navy is to the U.S. government. The reason Starfleet is heavily human is that it's the humans' military. The Vulcans have a fleet as well, and in the later series/movies, the Klingon fleet was also part of the Federation but not part of Starfleet. Starfleet is diverse but it stands to reason that humans would play a central role.
Babylon 5 has this but less blatantly. Humanity's hat is that they build communities wherever they go; any other species would have built the Babylon 5 for their own use only.
- More blatantly, the card game has a human-only agenda (a victory condition) called "Leading the Races", which allows you to win by playing a human faction with lots of different alien species in it.
In Farscape, the very human-like Sebaceans are one of the two major powers in the galaxy. As it turns out, they actually are genetically-engineered proto-humans from way back. As for the main cast, though the human Crichton is the main character, he isn't the leader - when they finally choose one, it's D'Argo.
Stargate SG-1 in spades. Let's face it the Tok'ra and Asgard have been spinning their wheels for milennia - and the Nox, the Tollan and the Ancients aren't even trying. But when four man teams of Earthpeople get in the mix we get solutions for problems like the Goa'uld, the Replicators, the Ori, the Wraith...! Sure, we cause a lot of new problems too, but hell, we get things done! Defenders of three galaxies people; At least the Ancients, Nox, Furlings and Asgard supposedly had each other to lean on for active help.
- The Nox and the Tollan are understandable candidates for the "not trying," award, but to lump the Ancients in with them? The ancients have been extinct for about ten thousand years, as of the current time. The very threat of Asgard intervention put a massive damper on Goa'uld expansion and kept them in check, while the Tok'ra kept the System Lords in a state of semi-constant war for most of their history. Were it not for these factors, Earth might have been conquered long ago. Still, the humans of Earth managed to take down the Ori, Goa'uld, and Replicators less than twelve years after their first off-world mission.

Tabletop Games

Dungeons and Dragons: In early editions, only humans were allowed to be Paladins, the natural party leader class. This was Justified by the D&D universe being "humanocentric", with humans as the most dominant race. Later explanations fleshed the concept out more, in that humans make up for their short lifespans and lack of specialized ability in any given area (elves for magic, dwarves for blacksmithing, etc.) with an ambition and drive longer-lived races lack and a knack for being able to become skilled in almost any profession, in essence becoming an entire race of Jacks Of All Trades. By comparison, dwarves tended to not be very skilled at magic, halflings weren't the most skilled fighters, etc.
Traveller. Humans rule most major states. This is because humans are better organized, more ambitious and more militarily efficient then others. And thus Asskicking Equals Authority. All three Imperiums were human led, though there are many of other species among the Imperial nobility.
In the Pen and Paper World of Warcraft D20 RPG, humans had bonuses to their diplomacy.

Video Games

In the Master of Orion series, the humans tend to be average in terms of most stats (though having a slight edge in research overall except against the Psilons), but they have a massive diplomacy bonus that allows them to easily make friends with all other races (who tend to have at least one major rival each) as well as the ability to get benefits from trade treaties much more quickly.
- The background information for Master of Orion III shows that it was a human-led alliance that destroyed the Guardian. Of course, the humans then took the lion's share of the spoils, much to the chagrin of the other races. Humans were also instrumental in stopping the Antareans (or so they thought).
Likewise in the Galactic Civilizations games, the Terran Alliance has an edge in diplomacy over most other races.
Things essentially end up this way in Mass Effect whether or not you kill off the council. Humanity shakes up most of Citadel Space's politics, military defense, and home security, both by its flaws and strengths. In a sense, humanity is the ultimate anti-complacency factor, as complacency is probably the Council's greatest flaw: they love putting hats on everything and each species eventually settles into one. However, humanity's role as a Jack of All Stats makes their only hat a refusal to have a hat.
- The exact process depends on the player character, but the end result is the entire galaxy acknowledging that humans - specifically this Memetic Badass they've given the galaxy - get results. Paragon Shepard is the more understanding, "we need to earn respect" type, while Renegade Shepard is...quoted above.
- Humans Advance Swiftly is also present, as it took humanity a grand total of 30 years to go from First Contact to a seat on the ruling Council. The Council has existed for millenia, and every other sentient race joining the galactic community was just made a client race (save the Turians, who got their seat for almost single-handedly putting down the Krogan Rebellions). Humanity basically blusters its way in by showing up, expecting to be given a Council seat, and then getting annoyed that it's taking so long for the Council to catch up and do it already. And it works!
The Reconstruction justifies it through a lack of competition. Of the other two sentient species in the setting, the shra have a tendency to follow whoever seems strongest, the fortians don't care much about outside affairs, and the fih'jik are traditionalistic to a fault, leaving humans as the primary explorers and leaders.
- It's also subverted, since The Hero is a shra. Could be Double Subverted, though, since he's an extreme subversion of most fantasy heroes and doesn't actually do much leading.
Although there are several different human species in the Elder Scrolls series, the Empire that controls the continent of Tamriel is run through all four games in the main series by an Imperial, a human, and all past Emperors in the Empire's history have been Imperial bar one.
- This is partially because the empire had been run by the same dynasty for its entire history, this dynasty was Imperial so it is logical that only Imperials would become emperor.
- However, a lot of this is because of the setting the games take place in. Tamriel is just one continent on the planet that TES takes place, and the others are ruled by many other races. In past eras, in fact, elves ruled the places humanity currently inhabits. There's a chance that the rule of mankind could end just as well, and the Aldmeri Dominion are bent on making making that chance happen.

Western Animation

Probably a coincidence, but for a short time Bouncing Boy is designated as leader for the Legion of Super Heroes. Guess which planet he's from. Go on.
A Slight variation: Teen Titans. There is only one alien in the group, Starfire, and a half demon, Raven. But Beast Boy and Cyborg have powers. Robin, the only completely normal Human on the team, is considered leader.
- Justified Trope since Robin is a strategic genius.