Someone is interesting because they excite your curiosity or somehow manage to capture your interest; your attention; your imagination. Whether we're online, on the phone, privately or in public, we've all at some point in time met someone who captured our interest/found interesting.
The most interesting person that comes to mind for me was a radio personality who I met (when I was much, much younger) at a broadcast of " The Colgate Cavity Fighters Club". She was interesting to me because, I've always heard her on the radio and wondered what she would be like in real person. She was AWESOME! How about you?

Who is the most interesting person you ever met? Why did you find them interesting?

I met a lady that is one of the heads of Womans Aid, a charity in the Uk for abused women,She was very engaging and her drive was something else,I walked away from her and was in awe of everything she does to strive to achieve her beliefs. I have met several interesting people, in real life, and many more on the net (Some of those I have met for real too).