You can in fact define an RPG, but you have to ask why is an RPG, not what is an RPG. If I dont create the character, Im not, by definition Role Playing.
Sure you are.
There is no law or rule which defines 'Role-playing' as playing out the actions of a custom-tailored character. Or that that game MUST have a wall of numerical stats to tell you who you are. There is no literary or literal or even implied definition to suggest this. Role-playing is, by it's simple English definition, stepping into a role or character other than your own.
There are plenty of Role-Playing games in which the character is made for you. Custom characters are not inherent in RPGs either.
The question of "Why" is a matter of philosophy... and we could debate it all day without gaining any ground. If you are unwilling to accept anything other than your rigid definitions and reasoning... and I am unwilling to yield to them... what could we hope to gain? I think instead that I will make a the same valid point I made in my last post:
There's room for the genre to expand, and embrace new ideas. This concept of sticking to 'tried-and-true' methods is the REASON idiot-sponge games like Call of Duty 9 have come to be. They STOPPED expanding beyond a single formula... and true-to-form... they have reached a level of stagnation. Even the die-hards have begun to taste the repetitive spoon-feeding of non-changing mechanics and barely-improved improvements.
One game after the next, with all the same mechanics and a different skin, does not a good game make.
You can do that to any genre... Real Time Strategy... Role-Playing Games... Turned-Bases Strategy... after a while, if you don't seek new ways to make the game differentiate from the last... you find yourself in a game-development quagmire... where you keep shoving in tried-and-true mechanics in order to keep the player from seeing through the thin veil:
This is just The Legend of Questdom: Insert Variable.
-addendum-
You're right. Some will call it elitism. Because it is. That is the pure definition of it. You seem to have this belief that RPG's are your domain... that you and your like-minded kind alone get to dictate to the world what a Role-Playing Game must be... and then proceed to insult anyone who disagrees with you.
If your RPG genre is dying... it is a death I wholeheartedly welcome... because there's no place in it for anyone who doesn't think just like you. Games are supposed to be fun, and interesting, and enjoyable.
When folks come along and demand that they know what is good, and everyone else is wrong... it is a disgrace to the term 'gamer'.