"Munich" was much more successful as a piece of entertainment, with an exciting thriller plot and more fully developed characters. The people in "Syriana" are just pawns in a diplomatic game, and maybe that's the point, but it doesn't make them interesting to watch. Moreover, when the filmmakers attempt to add human interest (e.g. a family tragedy befalls Matt Damon's character), it doesn't work. The ending sequence is nicely suspenseful, and ties some of the disparate plot lines together, but the movie takes much too long to get there.
The worst (that is, the most boring) of the four story lines is the one where Jeffrey Wright plays a lawyer investigating possible corruption in an American oil company merger. It's very difficult to make this kind of material cinematic, and writer/director Gaghan doesn't succeed. Many of the characters involved in this plot make speeches that are meant to be thought- provoking, but they come out of nowhere and are just as quickly forgotten. Better is the story about the young man training to be a terrorist: it's easy to follow, and shows us something not usually depicted in movies. Still, sandwiched between the other plot lines, it feels like a shallow exploration of how terrorists are made.
George Clooney, with his beard and weight gain, is certainly unrecognizable in his role as CIA employee Bob Barnes, and his acting is competent. But if he hadn't been involved in "Goodnight and Good Luck" this same year, I doubt he would have won the Oscar for this performance. Even here, he is outshone by Alexander Siddig, who plays Nasir, a reformist Arab prince. In a movie that tries to show the complexities and gray areas of Middle Eastern oil politics, Nasir is perhaps the most complex of all: spoiled and ambitious, but with noble ideals.
Also, for a movie that wants to be an intelligent exploration of the oil industry, why is the Iraq war mentioned only once, in a throwaway line?