Yeah, I got along pretty well with my exes' parents. I figure it's because I'm a relatively outgoing girl, I get good grades, I go to church, I don't do anything crazy, etc. In a nutshell I'm just average. And I suppose parents can't really find anything wrong with average kids. Especially if you go to the same church.
My parents never knew I was going out with anyone, but they did know the people and they were on pretty okay terms with them. My parents are rather conservative Chinese, so they typically like anyone who's a good student, God-fearing and knowledgeable.