Above is the intro to Lord of War. Below, due to embedding being disabled, is the link to City of God.
The Lord of War intro follows the life of a bullet. From construction to finally being fired. Where as City of God concentrates more on a animated style of sequence. There is lots of CGI used in the making of the Lord of War intro. Which contrasts the entirely animated City of God sequence.
Both of the sequences have quite happy music as well, creating a sense of tension as the audience know that they are about to watch quite a violent film (which in the cases of both films, is true). They use the music to completely contradict the ethics and theme of the film. To make the audience think. Or to bring out the fact that what they are about to see is only for entertainment and is not real.
The titles from Lord of War are very simple in themselves. They are simply fading in and out white text. This is so the audience is not distracted by them too much so they can watch the sequence that is being played. The intricate sequence is always from the same perspective as well, almost as if the audience were the eyes of the bullet. This makes it all the more shocking when it is fired, and this innanimate object that has been the central role of the film so far is fired and kills someone.
That kind of introduction is very different to the unspecific classic title sequence that is in City of God. It is a series of images that have been strongly tinted orange (a generally happy colour) which correlates to the grey, depressing atmosphere in the Lord of War sequence. The ending is very similar however. As in Lord of War, the sequence and music ends on a gunshot. Suggesting that the music player has been killed. And to bring the audience back down to earth, involving them more in the film.