I don't particularly care about UN resolutions either. Its being demonstrated pretty clearly that they're not much interested in actually enforcing them. Nevertheless, the widespread international support represented by the UN resolution is significant: it suggests that the situation in Iraq IS a concern to everyone, not just the U.S. It isn't just our interests that are in play here, though that alone should be sufficient justification. I think you're forgetting that our last three presidents have had to contend with Hussein, that terrible oppression is exercised by his regime, and that not too long ago, he invaded and plundered a neighboring country, and allowed murder, rape, and pillage to be inflicted on its population.
In any case, I think Tony Blair made the argument as to why Iraq poses a threat: there are weapons of mass destruction in the hands of someone who is an avowed enemy of the U.S., in a part of the world teeming with terrorists of a similar bent who are willing to die in the delivery of a weapon. Sooner or later, the two are going to find each other. The world (and the U.S. in particular) can't sit around and wait until they do find each other before it does something about it.
When you look at Hussein, his appetite for weapons of mass destruction, his hostility toward the U.S., Israel, and even his Arab neighbors, the prevelance of terrorists and countries that are permissive towards them, and the suicidal inclinations of those terrorists who would barely think twice before killing themselves in the delivery of a weapon - its hard for me to understand why there are still so many who can't see why we need to remove Hussein, scour Iraq for weapons, and help them move toward a more democratic society, or at least towards one which is less hostile to the U.S. and the world.