It’s strange how some games do not address character personality at all (or only very vaguely, like with alignment) while other games build PC characterization into the system.
If you look at several character sheets from different games, some give you insight into the character, and some don’t. Take a game like Mongoose Traveller for example. Traveller gives you no clue as to what the character is like. It’s all stats, skills and equipment.
Look at a Savage Worlds or GURPS character sheet. Drawbacks, disadvantages help define a character’s personality most of the time.
Is one better than the other?
I’m not sure.
In my experience, character generation between these disparate systems tends to happen in opposite order.
When I roll up a Traveller character, I take a look at the completed character and try to determine what sort of personality this collection of numbers might have. If I make a character that can’t make a single survival roll, maybe he’s a little kooky and can’t hold a job. I’ll often let the different careers determine his personality as well.
With systems that have disads and drawbacks, it normally works in the opposite direction — even more so because they tend to be point-buy systems. I come up with a character concept and personality first, then buy the stats, skills, ads and disads to build the character sheet as close as I can to my concept.
Many people have a preference for one method or the other. I personally count myself as a point-buy, concept-first player.
Then again, I’ve had an enormous amount of fun playing character concepts I never would have consciously created.
I’ve also seen players build detailed character personalities that rival anything created in a detailed chargen system, using a game that stays completely away from characterization, DnD4e.
I think if a player has a tendency to come up with creative character concepts, it’s going to happen whether there are rules there for it or not.