' “THE ENEMY WE’RE FIGHTING is different from the one we’d war-gamed against,” Wallace, commander of V Corps, said during a visit to the 101st Airborne Division headquarters here in central Iraq."

This is not very surprising. In war game their opponent would have more knowledge of US tactics and have good ideas on how to at least somewhat counter them. Also the opponent wouldn't be a criminal. I don't think it's very wise to expect that any war game would be similar to reality, rather it should be thought of as practice for thinking outside the box and an opportunty to work out kinks in various tactics.
War is not a game- Saddam can't quit and try again. Saddam does not care how many soldiers die. Saddam doesn't care how many civilians die.