[Enpeze]

Originally Posted by rust

Now, let us take a look at a common (Wikipedia) definition of roleplaying ga-
mes:

A role-playing game (RPG; often roleplaying game) is a game in which the
participants assume the roles of fictional characters and collaboratively cre-
ate or follow stories. Participants determine the actions of their characters
based on their characterization, and the actions succeed or fail according to
a formal system of rules and guidelines. Within the rules, players can improvi-
se freely; their choices shape the direction and outcome of the games.

Can one do all this with D&D 4.0 ?

- assume the role of a fictional character: yes
- collaboratively create or follow stories: yes
- use rules to decide the success of actions: oh, yes
- improvise freely within the rules: well, yes
- shape the direction and outcome of the game: yes

Is D&D 4.0 a roleplaying game, according to this definition ?

Obviously, yes.

Do we need another, more narrow definition of what an RPG is ?

Not in my opinion, I have no idea what it could be good for.

So, could we let it stand there, please ?

I think you should first take a look at the 4e books before answering your own questions with "yes".