I haven't met a famous person I mean getting down to the level of conversation but I have seen many a political personalities and many a film actors too and one or two directors too during my to and fro flights from India or USA.
Your vote on this answer has already been received
I will tell you my experience in general. Most of the so called persons are not happy to meet you, unless it serves their purpose, like politicians at the time of election. And, naturally, if you impose yourselves, you are bound to get cold reception. On the contrary you will get satisfaction when you meet successful people in their field.