Actors

The problem of having big name actors play underachievers in movies. And not just underachievers, but losers, low income housing project dwellers, etc.

1) This actor or actress (I refuse to let go the female form) has appeared in other movies in which he/she is a super rockstar brainy ass kicking winner.

2) The actor's training to date has polished the performance to the point where there's still an element of lookit me I'm awesome in every move and gesture (unless you're Josh Hartnett, who's acting seems to say lookit me I'm awesome but still acts on the level of a high school play).

3) Promotion and hype makes people think the movie is gonna be about rockstar winners.

Will Smith tried to start out as a low income loser in The Pursuit of Happyness
Hilary Swank in P.S. I Love You
There was one more that really bothered me but now it slips my mind.

On the other hand, now that I think about it, Jack Black is a big name these days, and he's always playing a low income underachiever type. I'm sure there are other examples of people who can pull this off, but he does comedy, which means hammy, like Ethan Hawke in Before the Devil Knows You're Dead, only that was more of a tragi-drama not comedy, but definitely hammy.

Now I am rambling.