I think people are getting the wrong idea out of my post.. i'll make some small post here to try and explain better.
If you're a parent, buying your 6 year old daughter a game console, what do you get? Wii and DS.
When hes 10, what do you get XB360. wii.
I would assume half of the people who own a ds are under 15.
25% around 8-14.
(Western world)
why? price, brand recognition, saturatio of shovelware.
PSP GTA:China town wars..? I'm not too sure, its too kiddy in its graphics to appeal to most GTA fans, but maybe.
http://www.vgchartz.com/games/game.php?id=5165®ion=All is the highest selling portable core game.
EDIT: That is fine, I gamed when I was that age too, but let me tell you this, I never thought of which console to get based on the quality of the core games it had, even though I only played core games.. my parents just bought what was advertised more i guess.