are Iranians good immigrants?

many are.  some aren't

They are like any other group consisting of good and bad. They are better than right wing extremists. 

I've only known a few couples. And all of them have appreciated the chance given them. 

I don’t think you can define a good or bad immigrant by nationality or ethnicity. At the end of the day people are individuals

I've only known a few (usually professors in college), but not had any problems.