Possible spoilers follow for those who haven't seen the movie. You've been warned.
There are things about the movie that work. These types of movies usually go the same way, but having him face jail time of his own volition worked well enough. A super hero who could do anything and yet takes responsibility was an obvious way of drawing sympathy (especially since Will Smith is always so likable in all of his roles, even when he's an ass). His "escape attempts" were only partially effective. Having the guards so on edge was another way of creating sympathy (Hancock vs. a world that doesn't understand him as he is torn between responsibility and freedom), but it was all a little too obvious.
I think that the "venting" scenes really worked, however, because he never went all of the way. Admitting that he was an alcoholic was as far as he could go, and that was enough to effectively set up his redemption.
The humor of course held the entire picture together because it was so charming, which forced some emotional connection that the rest of the movie played on. I have to agree with everybody else who says that the second half kind of fell flat. They finally built up enough good faith with the movie, and then they go for something that any other super hero movie could have done. They almost took all of the novelty out of Hancock.
I suppose it wasn't all that bad. There were potentially worse outcomes. After all, the generic approach would have been to introduce an element that sets Hancock back and makes him question everything he has gone through. Then, through a predictable conflict, he is redeemed fully. That would have doomed the movie completely. But I think that there were still some interesting routes that could have been explored had they built on the first half a lot more than they did. It almost felt like the first half was just an exercise in character development so that you would give a damn when they turn the story on its head and introduce elements that couldn't stand on their own.
FTWer said:
I don't think YOU know what it means.
Pretentious usually means self importance. In movie terms that usually means that it's trying to be greater than it really is while forgetting about what constitutes good storytelling. Generally speaking, I don't think that neither action movies nor comedies really are pretentious, and Hancock is mostly a mixture of both. Overwrought, perhaps, but it's not making any sweeping claims that make you think that it's trying to tell something that it is not equipped to handle. None of the technical aspects get too big for themselves. It is what it is on the surface: a desperate, lonely super hero looking for acceptance.