"Maybe it takes more than 4 years to completely turn around a huge economic downturn that the entire world is still suffering from"
I would argue it sure does, and the idea that giving these companies tax breaks will make them hire more seems crazy, most of Wall Street is doing very well right now, many companies are sitting on lots of money. The problem is that companies do not hire because they have money and want to be nice, they hire to fill a need.
The real issue is that people are out of work and times are tight, people are not buying, and at times like this, companies cut employees not hire them. A stimulus is one way to get the ball rolling again, just long enough that people have money to spend and companies have to hire to keep up again.
But the real issue is that during the Bush years middle class incomes stagnated, and instead of helping the middle class we decided to give tax breaks to big companies, and then we fixed the game to help these big companies in ways that they had just no chance of real failure, and contrary to popular republican belief instead of them deciding to hire people because they are making so much money they put it in their pockets, again because demand did not really rise that is just extra money made.
At least Obama has been pushing the right direction, and would have done more if he could have.
I think there could be some really good stimulus ideas, training people for jobs in the United States Army Corps of Engineers or something that would not only provide some money during the time the train, but mostly get them ready to be hired again. Sure better than paying people not to work.