I'm a big fan of humans, and not just in the sense that I like the female variety rather a lot. I also think homo sapiens has a big part to play in fantasy role playing, especially if pulp and Sword & Sorcery are your thang. You won't find orcs, kobolds and ogres fighting Conan or Elric. For Sword & Sorcery it's pretty much humans or Freakish Things, all the way.
What I like about humans and fantasy role playing is that they can mess with the players' thoughts and feelings in ways that demihuman races often can't. The average D&D gamer isn't much concerned about the mass slaughter of orc children or the murder of kobold pensioners, but give them human foes and they often start to think in more moral terms (albeit only very slightly) about the consequences of what they do. Villains who the players can empathise with are always more interesting than those with whom they can't.
Humans are also scarier than orcs or trolls, say. Players know what orcs are: they're evil and they want to kill you. Maybe torture you and eat you alive. But that attitude is expected and the response is obvious - total war. Kill or be killed. Humans on the other hand have nuance, and when dealing with them the only expectation can be that something unexpected will happen. This can be frightening, especially if you know that humans are just as capable of evil as orcs are - just in less predictable ways.
For that reason I always wanted a bestiary for a fantasy role playing game given over entirely to varieties of human. It could contain everything from Inca priests to Danish stevedores. Cultists, pirates, brigands, priests, labourers, butchers, the lot. Crazed wizards and brain-eating cannibals. That I never found such a bestiary is a source of great regret to me.
Maybe I'll make one some day.