Recently I've been developing a lot of prototypes that have characters in them. In creating various kinds of gameplay, I've noticed something interesting. I've been trying to come up with a short description of it, and here's my best attempt:
The more a character forces the player to adjust to the character, the more the character feels like an interesting person.
This is a bit of an unsupported statement if I just let it stand, so let me go into a bit more detail.
I developed two Power Rangers ripoff prototypes. In the first one, you controlled the heroes - told them which fights to fight and gave them turn-by-turn orders. However, because the rangers were basically faceless spandex stuntmen, they didn't feel like people. The monsters ended up feeling significantly more interesting!
The second prototype I created was about supplying the rangers with gear. You didn't get to choose their fights - they showed up, told you what enemy they were fighting, and you had to decide which equipment they should take into battle and how quickly to make their robots available. The equipment wrangling was actually kind of interesting, especially the robot side, since every new system you attached took more prep time... but a surprise side effect was that the heroes ended up feeling like characters. Although their traits and behavior were both simplistic and largely random, it was very easy to start to empathize with them and their efforts.
I think this was due to the afterbattle briefings I put in. You could debrief a ranger and it would show how well the various pieces of equipment and systems performed in the last fight - a necessary method of getting feedback. In turn, you would be able to refine your loadout so it would be better next time. In the background, the other four rangers would chat while you did this - randomized nonsense driven by their three traits. It made them feel surprisingly alive while also giving you information about what kinds of gear and systems you might want to give them (to match their traits).
Struggling to adapt my gameplay to the characters made it important for me to understand what the characters needed, statistically speaking. In turn, they became interesting characters to me, even though they were randomized nonsense in reality.
The Sims showed this to the extreme. While you do control your sims to a large extent, you spend a lot of time trying to rearrange your world to perfectly suit their needs. And, of course, people got really into it, even though the sims' "personalities" are basically randomized nonsense in reality.
You can even see this in things like Half Life, where the most popular character is the woman that leads you through a few tutorial sections. She's interesting not because she has anything valuable to offer, but because you have to play by her rules for a while. And, importantly, it's not just an escort mission: an escort mission is not about adapting to the character, it's about treating the character as a thing.
I'm sure you can see a lot of other examples, including perhaps partially explaining why boring villains (such as Sephiroth) become so popular.
So now I'm thinking about a whole slew of possible games where the point is to integrate well with characters. Hm!