Saddam is a consolation prize, which will keep Bush in office no matter who runs against him in the next election.
If they had pressed the issue of Bin Laden any longer, it would have begun to look like one of the greatest failures of the modern age. Imagine every resource of the most powerful country on the planet not being able to find one man travelling on the back of camels and horses.
We need a Hitleresque figure to personify Bush's political nightmare: "The Axis of Evil." Saddam fits that ideal perfectly.
And I agree with what Gil just said. I think we could have killed him in 1991, but now it isn't in our best interest as it will foster further terrorists attacks in his name down the road.
And as to comparing Castro to what is going on in the middle east, that's laughable. Castro may not have agreed with the US ideals for government, but he did what was in the best interest of his people.
The US mafia was raping Cuba, and would have continued to do so if Castro hadn't taken control. Under Castro Cuba has the highest literacy rate in the world, and one of the best health programs. If we hadn't placed an embargo on all their imports, they would probably be a highly developed society instead of a borderline 3rd world nation due to lack or resources.