I'm not a hacker, and actually don't even remember how I ended up here some day back in August 2009. I was one of those for whom the term "hacker" had a negative connotation.
I'm a designer and I didn't understand 90% of the topics discussed here. But the reason why I stuck around and why HN eventually became my most visited site, is the community's quality. Comment threads usually spawn multi-leveled discussions with various but not radical opinions about a topic. The top comment can slightly favor point A while its top answer moderates the tone with or without contradicting it. The result is a a discussion with various shades while most comment threads on other websites are generally black or white and favor one-liner jokes to in-depth opinions.
I believe Digg was still around in 2009 but was mostly focused on offbeat news. Slashdot never appealed to me. And even though reddit covers a lot of topics, the community isn't really open to discussion and/or criticism.
Although HN is mostly a tech news site, it oddly taught me more about arts, politics, business and lifestyle than any other website. I guess quality can't restrict itself to one single topic.