Well, we don't know the real persons behind majority of the usernames here. There may be some of us here who are famous in real life. So it's hard to tell, but as far as those who are personally known are concerned, at least there's
Charlie Lee, the creator of Litecoin. He's still a bit active. There might be more, but the rest of those who have got big names especially in crypto like Andreas Antonopoulos, Adam Back, Vitalik Buterin, and others are mostly inactive.
I would agree that Charlie Lee is likely the most famous person that can be reached on these forums. He has been featured on TV many times making him the most likely person to be recognized by the average person. There have been more influential and well known people who have posted here, but not many stuck around once the trolls and scammers moved in.