WW2 was a different kind of war. These countries had air bases and armies that could match ours. Something major needed to be done to end the war before the enemy could develop nuclear missiles.

Iraq is a lot different. Since the Saddam is no longer in power there is no point in bombing military sites. If we did major bombings we would just be killing civilians.

And isn't it mostly Iraqis killing each other with all the suicide bombings instead of us killing civilians directly?