NOT stats. Those are just a tool to better the roleplaying experience, as in quantifying certain characteristics that are harder to compare. They are in essence part of the rules of the game, so everyone is on the same level, and we can compare the effect of someone's punch versus another one's. They are not roleplaying. They are quantification of a role's attributes. They are not necessary.
The role
Roleplaying is taking a role and playing it (doh). So, the question to ask is "what's in a role?". What can differentiate roles? Characteristics of an individual and of his environnement. Someone always develops in function of his environement. So, we have personnality, experience, beliefs, social bonds, aptitudes and capacities.
Here we see where stats fails. Quantify social bonds, personnality, experience or beliefs. It doesn't work. It's even worse with an experience system where you level up and increase the characteristics.
Playing the role
Now that we know what is a role, we have to ask what is playing it. Playing it is making the character's actions (including thoughts, dialogue, motivations...) in function of the role. That's it. That means that personnality, experience, beliefs, social bonds, aptitudes and capacities are going to determine the actions.
A role evolves while playing it. A character's life experience is always greater after playing the role than before, but it does not have to impact on other characteristics such as personnality, beliefs, social bonds, aptitudes and capacities. Consolidation or redefinition of the role, it doesn't matter.
Standard stat systems include this evolution as experience points and whatever. The problem is, they are only attributed to aptitudes and capacities. While those are fine, they are not the essence of a role. A role is much more personnality, beliefs and social bonds than aptitudes and capacities. That's why the "role playing games" we play are sucky.
Defining the role
We know what's a role, and we know what is playing it. The next question is how is one role defined. Or, how much freedom does the player have when "creating" this role. In every roleplaying game, there is always a defined setting. There is also a defined situation, which might be, in some pnp game, at the player's discretion. One possiblity is letting the player take on any role possible within the boundaries of the setting, and put him in a situation, to which he reacts. The other way is handing the player a predefined role. It is similar to the precedent possibility, but the player has now to play the role within the limits of the setting, the situation and the role itself. Both possibilities work fine in a pen-and-paper rpg. Playing the role resides in guessing what would this character do in the situation, predefined role or not.
In computer roleplaying games, the second option is very limiting. Since the developpers are already guessing what the character would do in a situation and the character is predefined, you end up with a game that is pre-roleplayed. To permit roleplaying in this possibility, one has to make the defined role as less defined as possible, malleable. Hence the vault dweller, the nameless one... Part of their role is defined, part of it is left to the player. Roles that are completely defined, see Gordon Freeman or else, do not offer roleplaying possibilities. The role is already played. The game, in this case, is just the action between the preplayed roleplaying scenes.
Immersion
Immersion, just like stats, is a tool to facilitate roleplaying. It is, in a way, what permits the dissolution of self to let the role take all the place. Components that affect immersion are graphic style, sound, music, interface, rules of the game and player's interest. In a pnp rpg, graphic style, sound and music are left to the player's imagination, with some help of the gamemaster/storyteller. Interface is the player himself, which is the best interface you could have. That leaves us with rules of the game and player's interest in the setting/situations that affect the player's immersion.
In a cRPG, all of those components affect immersion, therefore there is a higher risk of fucking up. For example, night/day cycles and people's daily occupations are taken for granted in a pnp rpg, unlike in a cRPG. Things like climbing and jumping are pretty simple in pnp, while they are not in crpgs. You can always try to persuade someone even if you don't know how, but some rulesets do not permit you to do this, more often in crpgs. When immersion is broken by one of the component being bad or limited, the player's roleplaying suffers in return. Here is where we see that a living and reactive world is necessary to good roleplaying, as it is the determinant factor in immersion or "make believe". When the player fails to be immersed in the role, by not identifying to it or thinking about it as a role (by personnality, experience, beliefs, social bonds, aptitudes and capacities), the game ceases to be a roleplaying game. The best example: Diablo. Never does the player associate with the character he is playing, never does he thinks about it in terms of personnality, beliefs or social bonds. Therefore, it is not a roleplaying game.
Here we go.
A cRPG is an immersive game that lets the player play a role, inculding personnality, beliefs, social bonds, aptitudes and capacities, where the role is partially or entierly defined by the player to permit the roleplaying. The player has to be aware he is playing a role different than himself, and has to dissociate himself from the role voluntarily.
Well, I guess that's it. I'm sure I missed something, but it's all out of my mind right now. Heh