"Win Win" is a gem of a movie with a seemingly slight but sharp story and great performances led by Paul Giamatti.
Dick and I have been watching Paul Giamatti movies for years. Dick became a convert with "Private Parts." While I enjoyed Giamatti's role in that movie it was his role in "The Negotiator" which won me over and moved him off the list of actors I recognized and saw in lots of little parts, to an actor I watched for.
There's a reason directors seek out this actor sans "leading man looks." Watch Lady in the Water.
Every generation has its Charles Laughton, allowing for stylistic changes in acting and audience shared knowledge. Paul Giamatti is this generation's Laughton: an actor with range and intelligence and the ability to get an audience to espouse a point of view and connect. Even if it's just with a "throw away" glance.
Heart throbs can't do that because their good looks distract you in that momentary glance from the forward progression of the plot. (Cary Grant is excluded from this, because while some consider him a heart throb I don't, as he was so obviously so much more.)
It takes an actor who can project humanity (whether insane, manic, sad, or grumpy) to suck you in to the business at hand: the story. And at the same time give that story a face—it's always the same face, but the craft is, it really isn't.