Saddam's failure to comply with 17 UN resolutions passed under CHAPTER VII rules of the UN is not a half truth or a lie, it is a FACT!
For 12 years, everyone tried another way besides military force to bring Saddam into compliance. These actions failed. Military force was the only option that would ever bring about compliance with the resolutions given Saddam's unwillingness to cooperate. Oh, and no those resolutions were not just pieces of paper. Its to late for several hundred thousand Iraqi's, but fortunately its not to late for potentially several million people that could have been killed by Saddam in the next decade especially if he had developed nuclear weapons.
BUT, to the topic of this thread and it is an interesting one. There is not going to be and invasion of Syria, Iran, or North Korea, chiefly because the reasons and conditions for the invasion of Iraq do not exist in the way or to the degree that they do in the other countries.
Syria: Syria does have a past of invading Israel and occupying parts of Lebanon. But unlike Iraq, Syria has not invaded any countries in the past 20 years where as Iraq has attacked and invaded 4 different countries. Syria has extensively supported Hezebolah and other terrorist organizations responsible for terrorism in Israel. But its behavior for the most part is not nearly as threatening as Saddam's Iraq. Feeding and giving a few dollars to terrorist is one thing, Invading and occupying countries unprovoked and using chemical weapons against other countries is another. Syria is a country that needs to be looked at, but at the time being is not a candidate for regime change. Hopefully it will never make that list. Syria is to geographically seperated from the Persian Gulf to mount an effective invasion of the area and has to worry about Israel, which takes away from any insane effort to occupy the rich oil fields of the Persian Gulf.
Iran: Iran unlike Syria is much better positioned for an oil field grab. But Iran does not have a history of invading other countries. It did have plans after it was invaded by Iraq to defeat Iraq and not stop there, but that was in the few years after the Iranian revolution when the situation was constantly evolving. Like Syria, Iran has not invaded any country in the past 20 years(Except Iraq, but lets not forget it was Iraq that started the war). Iran's conventional military in terms of weapons is much smaller than Syria or Iraq. It is still primarily an infantry based military although it has purchased 800 tanks from Russia over the past 13 years. Iraq rebuilt or until then guarded by US troops will be able to deter any Iranian Aggression. Iraq blocks Iran's access to oil fields in Kuwait and Saudi Arabia. In terms of capability, Iran is less of a threat than Iraq was and Syria is. Its geographic proximity is not relevant as long as Iraq can remain a strong buffer. Its behavior is not even remotely suggestive in the way that Iraq's behavior was. More importantly, there have been many changes in Iran over the past 20 years. Slowly, people are getting more rights, but very slowly. There is not a single person in the Iranian government where all the power is located, unlike Iraq. There are progressives, conservatives, and moderates. Over the next 10 years there will be a huge population boom in Iran and hopefully, this youth can help bring about more change with a government that is not closed off to it, or dictitorial in the way Saddam's regime was. Like Syria, the main concern with Iran is its support for terrorism, primarily against Israel. Their nuclear ambitions are also a great concern, but again, this concern is moderated by its past behavior in regards to direct invasions and attacks on other countries, of which it has done neither unlike Iraq.
North Korea: Is a well armed Giant compared to Iraq prior to Gulf War II. Its posture is very threatening until you look at its history over the past 50 years. 50 years of no invasions of other countries. Some say geography has played a role in this and maybe it has. If thats the case, geography is not going to stop playing that role in the future. Unlike Saudi Arabia and Kuwait vs. Iraq , South Korea, China, and Russia can prevent North Korea from overruning their countries. But the fact remains that North Korea's past behavior is not threatening when compared with Iraq's past behavior. . It is a fact, even without nuclear weapons or WMD, that North Korea could kill over 200,000 South Koreans at a minimum the first day of a war. This is because 80% of North Korea's 11,000 toobs of artillery are all in range of Seoul's metropolitan area of 15 million people. Seoul is only 25 miles from the DMZ. This is the only place in the world where this unique condition exist. The artillery is well hidden in the mountains with many of the large guns protected by large hidden concrete doors that open when the weapon is ready to fire. The US military could eventually take out and destroy this artillery, but it could take several days if not weeks. The civilian loss of life in South Korea could pass a million during that time. This is without the use of Chemical, Biological or Nuclear weapons. Add those in, and the number of civilians killed jumps even higher. Because of North Korea's relatively good past behavior plus its enormous capability that could cause massive loss of life in the South in just a day, the cost of invading North Korea for outweighs the cost continueing to deter it.
To sum up none of these countries have behavior's that rise to the level of Saddam's regime.Syria,Iran are less capable than Iraq was for both military and geographic reasons. North Korea is more military capable than Iraq was, but is not geagraphically situated to do much.
Unless something were to radically change, there is not going to be any invasions of Syria, Iran, and North Korea. Iraq always was the most threatening out of all four do to its behavior,its military capability and geographic location. Saddam's regime was a unique threat to the world which is why it had to be overthrown.