I think the way this question is being framed is flawed.
RPG characters shouldn't be compared to real people. No game I ever played was intended to accurately model real life. If you're super-smart in a fantasy game you end up a mighty wizard, either protecting the world or attemping to dominate it. You don't graduate from college at 12, find you can't deal with life, and end up underemployed obsessively memorizing train schedules, which has been known to happen IRL...
Heck, The Sims is a better real life simulator than any RPG...
Now RPG's are meant to simulate certain kinds of fiction, but even so, there's one critical difference that invalidates comparisons between game characters and characters in fiction. In fiction, one person is in more or less complete control of every situation/obstacle and its outcome. In game, one person sets up the situations, and the outcomes are dependant on several peoples actions, facilitated by a set of mechanics which are based on probalities, on die-rolls.
So its meaningless to talk about the successes of a "average guy" hero in a novel, but there is ultimately no chance he can fail, if that's the authors intent. Fictional characters don't need the deck stacked in their favor, because the whole thing is rigged from the start. A fictional character can be deaf, dumb, and blind and still play a mean pinball.... A game character in the same boat would be toast --unless he was psionic, could see be radar, etc...
Now I'm not against low point buys {I currently play a d20 Mod. character built on 25}, and I'm all for challenge, its essential to the game. But that's just one way to ramp up the games difficulty, and it does perclude a kind of naked power-fantasy style of play, which ultimately, is built into any interation of d20.