Appearance-wise, humans in GW2 are much like their real-life counterparts. Ability-wise, there's very little resemblance - they can use magic and perform amazing feats of endurance and agility. Fighting simply to maintain a foothold in this new world, most of the humans are gathered under the banner of queen Jennah. The humans maintain their faith in the six gods, despite their silence.
Humans are a staple of video games, and GW2 is no exception. In the original Guild Wars, humans were the only playable race, and the game took place just after the height of their expansion. In Guild Wars 2, we're seeing the humans after the dragons, charr, and other races have fought them back. Centered in Divinity's Reach, and up until lately still fighting the Charr from their fortress Ebonhawke, humans are still fighting for their place in this harsh world.
As for internal enemies, not all the humans are united under the queen. There is a complex political landscape within human society where other political groups fight to gain the leadership for themselves.
We're used to humans, we know what they can do, so the main thing a game can do to make their humans unique is to give them a good story. The humans in GW2 are, for the most part, people who are working together to survive and thrive under adversity. They've had a challenging 200 years and now that they're finally working with the other races there might be a ray of sunshine in their sky.
Other than this crazy dinosaur thing in an fps, I've always played games as a human when given the choice. I tend towards characters are like me, which is why all my gw characters are female (but not why they're all short). This makes it pretty likely I'll have a human in GW2.
Read more about Guild Wars 2's humans on guildwars2.com's human page.