This is not an easy question to answer. While in the negative it can always be said that you should not just stick with cheap third party coverage, it is not easy to say exactly what you should cover. Should you do collision coverage as well as comprehensive, or should you only retain collision coverage? There are also other types of coverage like GAP, and you should have some knowledge about all of these, and your particular situation, before deciding how much coverage to buy.
If a car is so old or so badly damaged that it will cost more to repair it than to buy a new one, its owner should, or should have, bought gap coverage. If you consider the likelihood of natural disasters in your region to be low, you may choose to opt out of comprehensive coverage. Collision coverage, however, is a must, because when an accident takes place, that is what cars do, they collide. This has more chance of happening to a car than its getting stuck by a lightning bolt, for example; so, in order to gamble less but gamble sure, collision coverage is a must.
If your region has a tendency to produce various so called "acts of god," like floods, tornadoes, lightning and what not, you will want to consider comprehensive coverage. This takes care of all non-collision accidents like the ones mentioned above.
Finally, it all depends on your particular situation; there are no preset rules about it. The best way to go? Find out a good car insurance agent who talks straight, then talk to him. He will be able to help you out best with how to make a choice in buying coverage.