Like many women, I went through a horse-adoring phase, but after a halcyon adolescence spent shoveling manure and being kicked in the head, reality set in and I could no longer find the time or money to ride. Luckily for me, horses are rapidly becoming a regular feature in videogames, gracing everything from Mount and Blade to Suikoden III to Gallop Racer to Ocarina of Time.. But while the use of horses shows advancements in graphical quality and AI, very few games actually treat horses as what they are: living creatures that can be characters in their own right, and that have a huge impact on the player's experience.
There are ways for horses to function both as gameplay elements and as individuals.
I'm not sure how many equestrians are gamers (or vice versa), but I know that those of us who are often end up cursing under our breaths whenever we play a videogame that features riding. The horses don't act naturally, they're mechanical, they're mindless, and this destroys our immersion. It's a shame, because the proper use of horses in a game can hugely increase immersion, whether the player is familiar with the animals or not. I'm not saying we need to go through the half-hour long process of grooming, saddling, rubbing down, etc. that one would with a real horse (though I for one was tempted to whack John Marston upside the head every time he went to bed without unsaddling his mount), but there are ways for horses to function both as gameplay elements and as individuals.
There tend to be two ways in which games use horses: they either have one horse as a single, emphasized character, or they have multiple, interchangeable horses used as basic transport.
Nobody can deny that Epona was a huge step forward for the Zelda franchise. Remember that cute little filly following you around Lonlon Ranch? The surge of pride when you beat Ingo at the race? That adrenaline rush when Epona leapt over the wall to freedom? It was an incredible moment that established Epona firmly both in the Zelda canon and in the annals of gaming.
But is Epona really a character?
She was certainly useful, but let's look at her full role. Ocarina of Time, as an N64 game, may not have had the processing power to truly imitate horse behavior, so let's examine Twilight Princess. What, exactly, does Epona do? And I'm not talking about when Link was steering her around Hyrule - what does she do on her own?
Not one hell of a lot.
When Link wasn't on her back, Epona stands around, performs a few simple animations, maybe rears during a cutscene. Despite Twilight Princess' feature of horseback combat, Epona can't steer independently or perform any kind of autonomous actions.
Now, let's look at another individual horse: Agro, from Shadow of the Colossus.
He's one of only two major characters in the game, the other being the player character, Wander, and is necessary from a gameplay perspective. It is impossible to complete many battles and, indeed, to properly traverse the landscape without Agro. Wander's isolation leads to a near-automatic bonding with Agro. Just think of the Companion Cube in Portal; in any other circumstances, it would have been a useless burden, but in that industrial wasteland it became a valued friend. But there's more to Agro than this.
I asked before what Epona did independently; let's put the same question to Agro. When not being ridden, Agro wanders around, he grazes, walks to water sources to drink. He gallops across the fields and rears up on his hind legs, the same way real horses will when they're turned out loose in a paddock. He follows Wander of his own accord, and comes running up to him after having a stretch. But even more interesting, let's look at the things Agro did while being ridden. Agro swerves to avoid cliffs or obstacles. He will occasionally ignore commands. During the battle with Dirge (the sand serpent), Agro is left to run independently while Wander shoots the monster's eyes. Agro does not need commands to act. Agro does not need to be steered around every obstacle. Agro acts of his own accord. It didn't surprise me in the slightest to find out that the game designers had studied horse behavior while programming Agro. Agro is a character, and because he is, it's easier to step into Wander's shoes, and be swept away by his isolation and his quest.