Are you the first poster ever on FO? Wow, 2005!
I think this messageboard first got any real traction back in 2003 (wow, ten years for it already), so no, I'm beat by a quite a few people. I think I was somewhere around the 20,000th member here. Not too bad considering it has hundreds of thousands of members now.
If we go with just the major senior members, that also have a crap ton of posts, have been on here consistently without any long absences thought the years, and have spent a lot of shear accumulated hours on the boards, I would have to image I'm near the top when those four factors are considered together. I still think Georges has me well beat though when it comes to that stuff. Of course he's a FreeOnes legend.