There are many insurance companies out there, and a 'good' insurance company will vary by your needs. A good place to start is to get quotes from a variety of companies and compare them, not only...
The General offers cheap monthly auto insurance because it has flexible plans. Liberty Mutual, Farmers, and Safe Auto also offer cheap monthly insurance rates.
The best auto insurance company is state farm. but this is just my opinion. You may find that the best for you is all state. it is really just a matter or preference.