A good score in the IELTS exam depends on the purpose of writing the test.
If you have taken the IELTS test for immigration, then a good score depends on the country and the visa category that you have applied for.
For example, if you are applying for an Australian PR, you need to score at least a 6 on each module (Listening, Reading, Writing and Speaking) to be eligible. However, a 6 on each module does not earn you any points for English proficiency. A score of 7 on each module gets you 10 points while a score of 8 on each module gets you 20 points which are the maximum.
If you are applying for studying overseas, then you should get a score as per the country and the University that you are applying for. Most Universities abroad require you to have an overall score of 6 or 6.5 to be eligible to apply.