It is one of the conceits of our race that we are quite full of our own intelligence. Hopefully, one day we’ll run across a vastly more intelligent species and be put in our collective place. But until then, we’ll keep on calling our own intelligence the best thing since sliced bread — something, I should point out, that our intelligence invented, and still thinks itself mighty clever for having come up with.

Orcs are a classic fantasy villain race. They are anthropomorphic, but vastly lacking in intelligence in comparison to humans.
In nearly every fantasy universe, humans are the smartest creatures around. Even elves, the high variety of which are frequently portrayed as wiser than people, are really just humans with pointy ears. If you don’t believe me, just ask a half-elf, or a quarter-elf, or a third-elf. Now compare that against all of the stupid races in fantasy universes: goblins, orcs, trolls, ogres, etc. They’re all so dumb one wonders how they even manage to put their armor on in the morning.
To make up for their incredible stupidity, these creatures are also given incredible strength. The human protagonists in the story must therefore rely on their cunning, their wit, and their intelligence to triumph over the enemies. Even magic is nothing more than a form of intelligence made physically manifest — the art of spellcasting is portrayed as an academic endeavor, in which the most studious become the most powerful. The concept of fantasy magic is the ultimate in human intelligence navel-gazing.
Even in non-fantasy media, the protagonists typically defeat their human rivals by outsmarting them. The movies in which the protagonist defeats his nemesis simply by beating on him more powerfully are few and far between — and of those that do exist, most of them involve sport, an activity so frequently fetishized by commentators that all connections to reality are lost. You simply can’t have a compelling story without a triumph of the mind. It’s understandable, really: while our eyes merely gaze at the movie screen, it’s our own mind that is truly watching it, and minds do harbor sympathies for other minds.
We value human intelligence so greatly because we are the only beings on the planet who possess anything close to it. When we triumph over a lion, a bear, or a hippopotamus in nature, we do so not by brute force, but through our intelligence. In one-on-one hand-to-hand combat, a fight against an elephant isn’t remotely fair. Allow the human use of a simple hand-held weapon such as a spear and the odds tighten considerably. Now give him a modern weapon that represents the apex of human intelligence — say, an F-22 joint strike fighter — and the elephant is easily reduced to a cloud of pink mist that has no chance whatsoever of retaliating against the human roaring away at Mach 2 a couple miles above it.
It is no surprise, then, that our fantasy worlds mimic very much the real world. Even though we make our villain fantasy races anthropomorphic (an orc is frequently portrayed as being a human with prominent boar features, for instance), even though we give them the ability to speak language, they represent nothing more than the animals of our own world, which we are used to accustomed to dominating completely. Are the fantasy creatures more intelligent? Certainly. It’s not a fair fight if the man-sized enemies don’t use weapons. But ultimately all that they really are is animals. No wonder fantasy story lines follow the races of player characters: humans, elves, dwarves, gnomes, and others — all of which are pretty much the same as humans, sharing the same relative physical weaknesses, but possessing the same mental prowesses.
So it makes sense that human intelligences are most entertained by the dealings of other human intelligences, and that is thus what our fictions focus upon. It makes sense that in our fantasies we conduct battle against either humans or animals, because that is all we really know about fighting against in our own world — except in fantasy even the animals frequently look like humans because we really are that obsessed with ourselves. Yes, we humans really are quite full of ourselves, but seeing the complete lack of alternatives, who can blame us?